Mold temperature adjusting apparatus/method and mold temperature control unit

ABSTRACT

A mold temperature adjusting apparatus is provided in which change-over timing of high temperature medium and low temperature medium is adjusted by a heat transmission delay in heating and cooling of a mold being taken into consideration. The mold temperature adjusting apparatus comprises a high temperature fluid tank and a low temperature fluid tank, a high temperature fluid supply system and a high temperature fluid return system between the mold and the high temperature fluid tank, a low temperature fluid supply system and a low temperature fluid return system between the mold and the low temperature fluid tank, a high temperature fluid by-pass system and a low temperature fluid by-pass system, a heat recovery tank connected to the high temperature fluid tank and a pressure adjusting device.

This application is a divisional of application Ser. No. 11/045,113,filed Jan. 31, 2005 now U.S. Pat. No. 7,323,127.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mold temperature adjusting apparatusand method by which a change-over timing between a high temperaturemedium and a low temperature medium is appropriately adjusted so as toshorten a molding cycle time. The present invention also relates to amold temperature control unit of the same concept.

2. Description of the Related Art

In an injection step of an injection molding machine, if a moldtemperature is low, a molten resin that is injected makes contact withthe mold while pressure in the mold is not elevated yet, so that a resinsurface rapidly solidifies and a surface of a molded article oftenbecomes coarse. This is liable to cause a problem that the molten resinis not sufficiently transferred onto a cavity surface of the mold. Inorder to avoid this problem, it is necessary to elevate the moldtemperature so that solidification of the surface of the molten resin isdelayed. On the other hand, once the resin is filled in the mold, it ispreferable that the mold temperature is lowered so that cooling isexpedited and the injection step cycle is shortened. In the recentmolds, there are devised and provided various mold temperature adjustingapparatus and methods by which such mold temperature can be quicklyelevated or lowered. However, as the mold generally has a large thermalcapacity, if large amounts of high temperature medium and lowtemperature medium as heat medium fluids are alternately changed over tobe supplied, it is necessary to devise a change-over means so that thehigh temperature medium and low temperature medium are not mixed witheach other. Also, it is necessary to provide a high temperature mediumrecovery means so as to suppress a heat loss of the heat medium.

In a conventional heating/cooling change-over apparatus, a recovery tankexclusive for the high temperature medium and a recovery tank exclusivefor the low temperature medium are provided. When a mold heating step isto be changed over to a mold cooling step, the high temperature mediumremaining in a temperature adjusting passage in the mold is pushed outfrom the temperature adjusting passage by the low temperature mediumnewly supplied into the temperature adjusting passage to be recoveredinto the recovery tank exclusive for the high temperature medium. Also,when the mold cooling step is to be changed over to the mold heatingstep, the low temperature medium remaining in the temperature adjustingpassage is pushed out from the temperature adjusting passage by the hightemperature medium newly supplied into the temperature adjusting passageto be recovered into the recovery tank exclusive for the low temperaturemedium. This is disclosed in the Japanese laid-open patent application1998-34657 as Patent Document 1, for example.

In another conventional example of a heating/cooling change-overapparatus and a mold heating/cooling change-over method, the number ofthe recovery tanks is reduced, whereby only the high temperature fluidis recovered so as to lessen the thermal energy loss. That is, there areprovided a high temperature fluid passage system comprising acirculating passage, a pump transferring a fluid and a heater heatingthe fluid and also comprising an opening/closing valve enabling achange-over of the high temperature fluid passage system between acommunicating state and a non-communicating state, a temperatureadjusting passage (a fluid passage provided in a mold, a fluid supplyand return passage), a recovery tank arranged in the high temperaturefluid passage system and a discharge valve discharging the fluid storedin the recovery tank outside of the system. Thereby, when the moldcooling step is to be changed over to the mold heating step, the lowtemperature fluid remaining in the temperature adjusting passage isrecovered into the recovery tank. Also, when the mold heating step is tobe changed over to the mold cooling step, the high temperature fluidremaining in the temperature adjusting passage is recovered into therecovery tank. This is disclosed in the Japanese laid-open patentapplication 2002-210740 as Patent Document 2, for example.

In the heating/cooling change-over apparatus of the above-mentionedPatent Document 1, there are needed two recovery tanks on the hightemperature side and the low temperature side as the fluid mediumrecovery tank. Also, the high temperature medium is left as it is in therecovery tank in the mold cooling step. Hence, the temperature isconsiderably reduced by a radiation and when this high temperaturemedium is returned into the high temperature medium passage, it is mixedwith a high temperature medium of which, temperature has been adjustedto an appropriate high temperature and there arises a problem that thetemperature is reduced.

Also, in the heating/cooling change-over apparatus and moldheating/cooling change-over method of the above-mentioned PatentDocument 2, while the low temperature fluid recovered into the recoverytank is discharged out of the system, the recovery tank is cooled by therecovery of the low temperature fluid so that the recovered hightemperature fluid also is cooled in the recovery tank. Thus, when thisrecovered high temperature fluid is recovered into the high temperaturefluid passage system, the temperature of the high temperature fluid isreduced and there arises a problem that the high temperature fluid is tobe re-heated in the high temperature fluid passage system so that atemperature adjustment is carried out.

SUMMARY OF THE INVENTION

In view of the above-mentioned problems, the present invention isproposed with an object to provide a mold temperature adjustingapparatus and method as well as a mold temperature control unit by whicha change-over timing between a high temperature medium and a lowtemperature medium is adjusted, wherein a delay of heat transmissionboth in heating and cooling of the high temperature medium and lowtemperature medium is taken into consideration so that a cycle time ofthe molding steps is shortened, temperature changes relative torespective set temperatures of the high temperature medium and lowtemperature medium are reduced and an energy loss is reduced to therebyobtain an optimal mold temperature in the injection step.

In order to solve the above-mentioned object, the present inventionprovides the following means (1) to (27):

-   (1) A first means is a mold temperature adjusting apparatus    comprising a high temperature fluid tank having a temperature    adjusting means adjusting temperature of a fluid to a set high    temperature, a high temperature fluid supply system having a high    temperature fluid transfer pump supplying the fluid of high    temperature into a mold from the high temperature fluid tank, a high    temperature fluid return system returning the fluid into the high    temperature fluid tank from the mold, a low temperature fluid tank    having a temperature adjusting means adjusting temperature of the    fluid to a set low temperature, a low temperature fluid supply    system having a low temperature fluid transfer pump supplying the    fluid of low temperature into the mold from the low temperature    fluid tank and a low temperature fluid return system returning the    fluid into the low temperature fluid tank from the mold so that a    control of a mold temperature of the mold is effected such that the    fluid of high temperature from the high temperature fluid tank and    the fluid of low temperature from the low temperature fluid tank re    selectively changed over from one to the other to flow through a    fluid passage provided in the mold, characterized in that the mold    temperature adjusting apparatus further comprises a high temperature    fluid by-pass system connecting the high temperature fluid supply    system and the high temperature fluid return system to each other, a    low temperature fluid by-pass system connecting the low temperature    fluid supply system and the low temperature fluid return system to    each other, a heat recovery tank having its upper portion connected    to the high temperature fluid tank and its lower portion connected    to the low temperature fluid supply system as well as having a means    preventing the fluids of high temperature and low temperature from    mixing with each other in the heat recovery tank and a pressure    adjusting system connecting the heat recovery tank and the low    temperature fluid tank to each other as well as having a pressure    adjusting means.-   (2) A second means is a heat recovery tank used in a mold    temperature adjusting apparatus, characterized in that the heat    recovery tank comprises an upper inlet/outlet port and a lower    inlet/outlet port of a fluid, the upper inlet/outlet port and lower    inlet/outlet port being horizontally constructed along an inner    surface of the heat recovery tank so as to minimize a vertical    dynamic pressure when the fluid is fed in or fed out, a multi-hole    plate provided in each of an upper portion and a lower portion of    the heat recovery tank so as to cause a flow resistance of the fluid    and a means maintaining a boundary between the fluid of high    temperature and the fluid of low temperature by a temperature    difference between them so as to suppress a convection of the fluid.-   (3) A third means is a heat recovery tank used in a mold temperature    adjusting apparatus, as mentioned in the first means, characterized    in that the multi-hole plate is formed in a cylindrical or polygonal    shape and is vertically provided in each of a tank high temperature    fluid side portion and a tank low temperature fluid side portion so    as to separate the vicinity of the inlet/outlet port of the fluid    and a tank body portion of the heat recovery tank from each other to    thereby construct the heat recovery tank such that the fluid    horizontally flows in and flows out through the multi-hole plate    from a circumferential direction of the tank and, where dl is a hole    diameter of each of multi-holes of the multi-hole plate and vl is a    flow velocity of the fluid flowing in the tank body portion from the    holes of the multi-hole plate, the heat recovery tank is designed so    that Ri represented by the following equation becomes 10 or more:    Ri=Δρ·g·dl/(ρmean·vl ²)    -   Here, g is the gravitational acceleration, Δρ is a density        difference between the fluid of high temperature and the fluid        of low temperature and ρ mean is a mean density of the fluid.-   (4) A fourth means is a heat recovery tank used in a mold    temperature adjusting apparatus, as mentioned in the second means,    characterized in that the means maintaining the boundary is a    plurality of rectifying plates vertically arranged with a    predetermined gap being maintained between each of the rectifying    plates.-   (5) A fifth means is a heat recovery tank used in a mold temperature    adjusting apparatus, as mentioned in the second means, characterized    in that the means maintaining the boundary is constructed such that    a guide bar is vertically provided being fixed to a bottom central    portion of the heat recovery tank, a float disc, having an outer    diameter slightly larger than an inner diameter of the heat recovery    tank and having its central portion fixed with a guide pipe of an    appropriate length elongating perpendicularly to a disc plane of the    float disc, is provided so that the guide bar is loosely inserted    into the guide pipe, the float disc is made of a heat insulating    material and has an integrated density of a middle value between a    density of the fluid of high temperature and that of the fluid of    low temperature and, when the fluid of high temperature is fed into    an upper portion of the heat recovery tank and the fluid of low    temperature is fed into a lower portion of the heat recovery tank,    the float disc moves up and down corresponding to an upward and    downward movement of the boundary between the fluid of high    temperature and the fluid of low temperature caused by feed-in and    feed-out of the fluid to thereby prevent the fluid of high    temperature and the fluid of low temperature from mixing with each    other.-   (6) A sixth means is a heat recovery tank used in a mold temperature    adjusting apparatus, as mentioned in the fifth means, characterized    in that the float disc is formed having a shape of a bag filled with    the fluid and provided being horizontally maintained by the guide    pipe.-   (7) A seventh means is a heat recovery tank used in a mold    temperature adjusting apparatus, as mentioned in any one of the    second to the sixth means, characterized in that a heat insulating    material is applied to or coated on an inner surface of the heat    recovery tank existing in the range in which the boundary between    the fluid of high temperature and the fluid of low temperature moves    up and down.-   (8) An eighth means is a mold temperature adjusting method in an    injection molding step using the mold temperature adjusting    apparatus, as mentioned in the first means, the injection molding    step being of heating the mold before filling a molten resin and    cooling the mold after filling the resin, characterized in that the    mold temperature adjusting method comprises the steps of: by    detecting a mold temperature T by a mold temperature sensor,    previously setting a heating over-shooting temperature correction    value ΔTH for a mold heating, a cooling under-shooting temperature    correction value ΔTL for a mold cooling, a resin filling start mold    temperature TH for starting a filling step, a mold opening start    temperature TL, an over-shooting time S1 and an under-shooting time    S2 as well as calculating a high temperature fluid stop temperature    TH−ΔTH by subtracting the heating over-shooting temperature    correction value ΔTH from the resin filling start mold temperature    TH and calculating a low temperature fluid stop temperature TL+ΔTL    by adding the cooling under-shooting temperature correction value    ΔTL to the mold opening start temperature TL; supplying the fluid of    high temperature into the mold via the high temperature fluid supply    system as a mold heating step; stopping the supply of the fluid of    high temperature when the mold temperature reaches the high    temperature fluid stop temperature TH−ΔTH as well as opening the    high temperature fluid by-pass system during the over-shooting time    S1 so as to cause the fluid of high temperature to by-pass; starting    the filling step when the mold temperature T reaches the resin    filling start mold temperature TH; closing the high temperature    fluid by-pass system after the over-shooting time S1 has passed as    well as opening a passage connecting to the heat recovery tank from    the mold; supplying the fluid of low temperature into the mold via    the low temperature fluid supply system so that the fluid of high    temperature remaining in the fluid passage of the mold is recovered    into the heat recovery tank via the high temperature fluid tank as    well as continuing a mold cooling step by supplying the fluid of low    temperature into the mold via the low temperature fluid supply    system; stopping the supply of the fluid of low temperature into the    mold when the mold temperature T reaches the low temperature fluid    stop temperature TL+ΔTL as well as opening the low temperature fluid    by-pass system during the under-shooting time S2 so as to cause the    fluid of low temperature to by-pass; closing the low temperature    fluid by-pass system when the mold temperature T reaches the mold    opening start temperature TL to thereby finish the mold cooling    step; opening the mold and taking out a molded article; after the    under-shooting time S2 has passed, recovering the fluid of low    temperature into the heat recovery tank by pushing by the fluid of    high temperature; and continuously supplying the fluid of high    temperature into the mold to thereby return to the mold heating    step.-   (9) A ninth means is a mold temperature adjusting method as    mentioned in the eighth means, characterized in further comprising    the steps of: in the mold cooling step and in a replacement step    replacing the fluid of high temperature with the fluid of low    temperature, closing the low temperature fluid by-pass system and in    the mold heating step, opening the low temperature fluid by-pass    system as well as continuously operating the low temperature fluid    transfer pump: likewise, in the mold heating step and in a    replacement step replacing the fluid of low temperature with the    fluid of high temperature, closing the high temperature fluid    by-pass system and in the mold cooling step, opening the high    temperature fluid by-pass system as well as continuously operating    the high temperature fluid transfer pump, so that temperatures of    supply pipings and return pipings of both of the fluid of high    temperature and the fluid of low temperature are maintained as well    as the fluid of high temperature remaining in the mold and the fluid    of low temperature remaining in the mold are recovered into the high    temperature fluid tank and the low temperature fluid tank,    respectively.-   (10) A tenth means is a mold temperature adjusting method as    mentioned in the eighth or ninth means, characterized in that    pressure in piping systems is maintained higher by the low    temperature fluid transfer pump being continuously operated as well    as by the pressure adjusting system so that a vaporizing temperature    of the fluid is maintained higher and the mold can be controlled in    a higher temperature.-   (11) An eleventh means is a mold temperature control unit performing    a control of heating the mold before filling a molten resin and    cooling the mold after filling the resin by the mold temperature    adjusting apparatus as mentioned in the first means, characterized    in that the mold temperature control unit performs the control    comprising the steps of: by receiving a signal of a mold temperature    T detected by a mold temperature sensor, previously setting a    heating over-shooting temperature correction value ΔTH for a mold    heating, a cooling under-shooting temperature correction value ΔTL    for a mold cooling, a resin filling start mold temperature TH for    starting a filling step, a mold opening start temperature TL, an    over-shooting time S1 and an under-shooting time S2 as well as    calculating a high temperature fluid stop temperature TH−ΔTH by    subtracting the heating over-shooting temperature correction value    ΔTH from the resin filling start mold temperature TH and calculating    a low temperature fluid stop temperature TL+ΔTL by adding the    cooling under-shooting temperature correction value ΔTL to the mold    opening start temperature TL; supplying the fluid of high    temperature into the mold via the high temperature fluid supply    system as a mold heating step; stopping the supply of the fluid of    high temperature when the mold temperature T reaches the high    temperature fluid stop temperature TH−ΔTH as well as opening the    high temperature fluid by-pass system during the over-shooting time    S1 so as to cause the fluid of high temperature to by-pass; starting    the filling step when the mold temperature T reaches the resin    filling start mold temperature TH; closing the high temperature    fluid by-pass system after the over-shooting time S1 has passed as    well as opening a passage connecting to the heat recovery tank from    the mold; supplying the fluid of low temperature into the mold via    the low temperature fluid supply system so that the fluid of high    temperature remaining in the fluid passage of the mold is recovered    into the heat recovery tank via the high temperature fluid tank as    well as continuing a mold cooling step by supplying the fluid of low    temperature into the mold via the low temperature fluid supply    system; stopping the supply of the fluid of low temperature into the    mold when the mold temperature T reaches the low temperature fluid    stop temperature TL+ΔTL as well as opening the low temperature fluid    by-pass system during the under-shooting time S2 so as to cause the    fluid of low temperature to by-pass; closing the low temperature    fluid by-pass system when the mold temperature T reaches the mold    opening start temperature TL to thereby finish the mold cooling    step; opening the mold and taking out a molded article; after the    under-shooting time S2 has passed, recovering the fluid of low    temperature into the heat recovery tank by pushing by the fluid of    high temperature; and continuously supplying the fluid of high    temperature into the mold to thereby return to the mold heating    step.-   (12) A twelfth means is a mold temperature control unit performing a    control of temperature of a mold by a predetermined high temperature    fluid and low temperature fluid being selectively caused to flow in    the mold, characterized in that the mold temperature control unit    performs the control comprising the steps of: by receiving a signal    of a mold temperature detected by a mold temperature sensor,    previously setting a heating over-shooting temperature correction    value ΔTH of the mold, a cooling under-shooting temperature    correction value ΔTL of the mold, a resin filling start mold    temperature TH for starting a filling step and a mold opening start    temperature TL as well as calculating a high temperature fluid stop    temperature TH−ΔTH by subtracting the heating over-shooting    temperature correction value ΔTH from the resin filling start mold    temperature TH and calculating a low temperature fluid stop    temperature TL+ΔTL by adding the cooling under-shooting temperature    correction value ΔTL to the mold opening start temperature TL;    supplying the high temperature fluid into the mold for heating the    mold; stopping the supply of the high temperature fluid when a mold    temperature T of the mold reaches the high temperature fluid stop    temperature TH−ΔTH; supplying the low temperature fluid into the    mold for cooling the mold; and stopping the supply of the low    temperature fluid when the mold temperature T reaches the low    temperature fluid stop temperature TL+ΔTL.-   (13) A thirteenth means is a mold temperature adjusting apparatus    performing a temperature control of a mold by a predetermined high    temperature heat medium and low temperature heat medium being    selectively caused to flow in a heat medium passage provided in the    mold, characterized in that the mold temperature adjusting apparatus    comprises a mold temperature sensor actually measuring a mold    temperature of the mold and a mold temperature control means    performing a control including the steps of; while the mold is    heated, stopping supply of the high temperature heat medium into the    mold when the mold temperature is elevated to a high temperature    fluid stop temperature TH−ΔTH obtained by subtracting a heating    over-shooting temperature correction value ΔTH from a predetermined    resin filling start mold temperature TH and while the mold is    cooled, stopping supply of the low temperature heat medium into the    mold when the mold temperature is lowered to a low temperature fluid    stop temperature TL+ΔTL obtained by adding a cooling under-shooting    temperature correction value ΔTL to a predetermined mold opening    start temperature TL, the heating over-shooting temperature    correction value ΔTH being a predicted elevated temperature value    regulating a supply stop timing of the high temperature heat medium    so that over-shooting of the mold temperature is suppressed, the    cooling under-shooting temperature correction value ΔTL being a    predicted lowered temperature value regulating a supply stop timing    of the low temperature heat medium so that under-shooting of the    mold temperature is suppressed.-   (14) A fourteenth means is a mold temperature adjusting apparatus as    mentioned in the thirteenth means, characterized in that the mold    temperature control means recognizes a progress of temperature    elevation corresponding to the heating over-shooting temperature    correction value ΔTH by the mold temperature sensor actually    measuring the mold temperature or by a timer means measuring an    over-shooting time S1 predicted as needed for the mold temperature    to be elevated to the resin filling start mold temperature TH from    the high temperature fluid stop temperature TH−ΔTH as well as    recognizes a progress of temperature lowering corresponding to the    cooling under-shooting temperature correction value ΔTL by the mold    temperature sensor actually measuring the mold temperature or by a    timer means measuring an under-shooting time S2 predicted as needed    for the mold temperature to be lowered to the mold opening start    temperature TL from the low temperature fluid stop temperature    TL+ΔTL.-   (15) A fifteenth means is a mold temperature adjusting apparatus as    mentioned in the thirteenth means, characterized in that the mold    temperature control means is constructed such that the supply of the    high temperature heat medium into the mold is started when the mold    temperature is lowered to a high temperature heat medium supply    start temperature set value TL+ΔTL2 obtained by adding a high    temperature heat medium supply start temperature correction value    ΔTL2, which is smaller than the cooling under-shooting temperature    correction value ΔTL (ΔTL2<ΔTL), to the low temperature fluid stop    temperature TL and the supply of the low temperature heat medium    into the mold is started when the mold temperature is elevated to    the resin filling start mold temperature TH.-   (16) A sixteenth means is a mold temperature adjusting apparatus as    mentioned in the fifteenth means, characterized in that the mold    temperature control means recognizes the time when the mold    temperature is lowered to the high temperature heat medium supply    start temperature set value TL+ΔTL2 by the mold temperature sensor    actually measuring the high temperature heat medium supply start    temperature set value TL+ΔTL2 or by a timer means measuring a low    temperature maintaining time set value SH predicted as needed for    the mold temperature to be lowered to the high temperature heat    medium supply start temperature set value TL+ΔTL2 from the low    temperature fluid stop temperature TL+ΔTL.-   (17) A seventeenth means is a mold temperature adjusting apparatus    as mentioned in the fifteenth means, characterized in further    comprising a temperature control condition setting means setting    mold temperature control conditions of the temperatures of the high    temperature heat medium and low temperature heat medium, resin    filling start mold temperature TH, heating over-shooting temperature    correction value ΔTH, mold opening start temperature TL, cooling    under-shooting temperature correction value ΔTL and high temperature    heat medium supply start temperature correction value ΔTL2 and an    image displaying panel displaying the mold temperature control    conditions in a molding step as well as displaying actually measured    temperature changes of the mold in an actual molding step.-   (18) An eighteenth means is a mold temperature adjusting apparatus    as mentioned in the seventeenth means, characterized in that the    image displaying panel is constructed such that the mold temperature    control conditions and actually measured temperature changes are    changed over to each other to be displayed on the same one screen.-   (19) A nineteenth means is a mold temperature adjusting apparatus as    mentioned in the seventeenth means, characterized in further    comprising a means predicting the heating over-shooting temperature    correction value ΔTH based on a time constant of temperature changes    of the mold when the mold as a single unit is heated as well as    predicting the cooling under-shooting temperature correction value    ΔTL based on a time constant of temperature changes of the mold when    the mold as a single unit is cooled.-   (20) A twentieth means is a mold temperature adjusting apparatus as    mentioned in the fifteenth means, characterized in that the mold is    a mold of an injection molding machine controlled by a molding    machine control means having an injection molding condition setting    and image displaying panel and the injection molding condition    setting and image displaying panel is provided with a temperature    control condition setting means setting mold temperature control    conditions of the temperatures of the high temperature heat medium    and low temperature heat medium, resin filling start mold    temperature TH, heating over-shooting temperature correction value    ΔTH, mold opening start temperature TL, cooling under-shooting    temperature correction value ΔTL and high temperature heat medium    supply start temperature correction value ΔTL2 as well as is    constructed so as to display thereon the mold temperature control    conditions set by the temperature control condition setting means    and actually measured temperature values of the mold in an actual    molding step.-   (21) A twenty-first means is a mold temperature adjusting method    performing a control of temperature of a mold by a high temperature    heat medium and low temperature heat medium of predetermined    temperatures being selectively caused to flow in a heat medium    passage provided in the mold, characterized in that the mold    temperature adjusting method includes the steps of: actually    measuring a mold temperature of the mold; and while the mold is    heated, stopping supply of the high temperature heat medium into the    mold when the mold temperature is elevated to a high temperature    fluid stop temperature TH−ΔTH obtained by subtracting a heating    over-shooting temperature correction value ΔTH from a resin filling    start mold temperature TH of a predetermined resin and while the    mold is cooled, stopping supply of the low temperature heat medium    into the mold (2) when the mold temperature is lowered to a low    temperature fluid stop temperature TL+ΔTL obtained by adding a    cooling under-shooting temperature correction value ΔTL to a    predetermined mold opening start temperature TL, the heating    over-shooting temperature correction value ΔTH being a predicted    elevated temperature value regulating a supply stop timing of the    high temperature heat medium so that over-shooting of the mold    temperature is suppressed, the cooling under-shooting temperature    correction value ΔTL being a predicted lowered temperature value    regulating a supply stop timing of the low temperature heat medium    so that under-shooting of the mold temperature is suppressed.-   (22) A twenty-second means is a mold temperature adjusting method as    mentioned in the twenty-first means, characterized in that a    progress of temperature elevation corresponding to the heating    over-shooting temperature correction value ΔTH is recognized by the    mold temperature sensor actually measuring the mold temperature or    by a timer means measuring an over-shooting time S1 predicted as    needed for the mold temperature to be elevated to the resin filling    start mold temperature TH from the high temperature fluid stop    temperature TH−ΔTH as well as a progress of temperature lowering    corresponding to the cooling under-shooting temperature correction    value ΔTL is recognized by the mold temperature sensor actually    measuring the mold temperature or by a timer means measuring an    under-shooting time S2 predicted as needed for the mold temperature    to be lowered to the mold opening start temperature TL from the low    temperature fluid stop temperature TL+ΔTL.-   (23) A twenty-third means is a mold temperature adjusting method as    mentioned in the twenty-second means, characterized in that the    over-shooting time S1 is predicted based on a time constant of    temperature changes of the mold when the mold as a single unit is    heated as well as the under-shooting time S2 is predicted based on a    time constant of temperature changes of the mold when the mold as a    single unit is cooled.-   (24) A twenty-fourth means is a mold temperature adjusting method as    mentioned in the twenty-second means, characterized in that the    supply of the high temperature heat medium into the mold is started    when the mold temperature is lowered to a high temperature heat    medium supply start temperature set value TL+ΔTL2 obtained by adding    a high temperature heat medium supply start temperature correction    value ΔTL2, which is smaller than the cooling under-shooting    temperature correction value ΔTL (ΔTL2<ΔTL), to the low temperature    fluid stop temperature TL and the supply of the low temperature heat    medium into the mold is started when the mold temperature is    elevated to the resin filling start mold temperature TH.-   (25) A twenty-fifth means is a mold temperature adjusting method as    mentioned in the twenty-fourth means, characterized in that the time    when the mold temperature is lowered to the high temperature heat    medium supply start temperature set value TL+ΔTL2 is recognized by    the mold temperature sensor actually measuring the high temperature    heat medium supply start temperature set value TL+ΔTL2 or by a timer    means measuring a low temperature maintaining time set value SH    predicted as needed for the mold temperature to be lowered to the    high temperature heat medium supply start temperature set value    TL+ΔTL2 from the low temperature fluid stop temperature TL+ΔTL.-   (26) A twenty-sixth means is a mold temperature adjusting method as    mentioned in the twenty-fourth means, characterized in further    including the steps of: setting mold temperature control conditions    of the temperatures of the high temperature heat medium and low    temperature heat medium, resin filling start mold temperature TH,    heating over-shooting temperature correction value ΔTH, mold opening    start temperature TL, cooling under-shooting temperature correction    value ΔTL and high temperature heat medium supply start temperature    correction value ΔTL2; and displaying on an injection molding    condition setting and image displaying panel a first image showing a    reference mold temperature curve of a molding step added with the    mold temperature control conditions and a second image showing    actually measured temperature changes of the mold in an actual    molding step.-   (27) A twenty-seventh means is a mold temperature adjusting method    as mentioned in the twenty-first means, characterized in that the    heating over-shooting temperature correction value ΔTH is predicted    based on a time constant of temperature changes of the mold when the    mold as a single unit is heated and the cooling under-shooting    temperature correction value ΔTL is predicted based on a time    constant of temperature changes of the mold when the mold as a    single unit is cooled.

As the invention of Claim 1 employs the above-mentioned first means,after the mold is heated, the fluid of high temperature is recovered notonly into the high temperature fluid tank but also into the heatrecovery tank. Hence, no surplus fluid of high temperature is needed tobe discharged outside and also the fluid of high temperature recoveredinto the heat recovery tank can be re-used at the time of moldre-heating. Thus, a heat loss of the fluid or heat medium can bereduced. Moreover, as a high temperature portion of the apparatus isalways pressurized by the high temperature fluid transfer pump andpressure adjusting system, the fluid is in no case vaporized.

As the invention of claim 2 employs the above-mentioned second means,the fluids of high temperature and low temperature can be recovered by asimple structure and making up of the fluid from outside becomes almostunnecessary.

As the invention of claim 3 employs the above-mentioned third means, thedesign is made such that the function Ri (Richardson number)representing the relation between the hole diameter of the hole of themulti-hole plate and the energy by the flow velocity passing through thehole of the multi-hole plate becomes 10 or more. Hence, in addition tothe effect of the invention of claim 2, irregularity of the boundarybetween the fluid of high temperature and the fluid of low temperaturein the heat recovery tank is reduced and mixing of the fluids can besuppressed.

As the invention of claim 4 employs the above-mentioned fourth means,the boundary surface area of the boundary generated by the specificgravity difference between the fluid of high temperature and the fluidof low temperature is separated into small units by the rectifyingplates. Hence, in addition to the effect of the invention of claim 2,mixing of the fluids can be further reduced.

As the invention of claim 5 employs the above-mentioned fifth means, inaddition to the effect of the invention of claim 5, the fluid of hightemperature and the fluid of low temperature can be completelypartitioned from each other by the float disc, and heat transmission tothe fluid of low temperature from the fluid of high temperature can bereduced.

As the invention of claim 6 employs the above-mentioned sixth means, inaddition to the effect of the invention of claim 5, the float disc ismade in the form of the bag filled with the fluid and the float disc canbe securely floated in the boundary between the fluid of hightemperature and the fluid of low temperature.

As the invention of claim 7 employs the above-mentioned seventh means,in addition to the effect of the invention of any one of the second tothe sixth means, heat escaping from the fluid of high temperaturethrough a wall of the heat recovery tank can be reduced and an energysaving effect can be obtained.

As the invention of claim 8 employs the above-mentioned eighth means,each change-over of the fluids is performed earlier by the time neededfor elevation of the heating over-shooting temperature as well as by thetime needed for lowering of the cooling under-shooting temperature.Thereby, the time of the molding steps can be shortened. Also, the fluidof high temperature and the fluid of low temperature are alternatelyreplaced with each other in the single heat recovery tank. Hence, thefacilities can be simplified and the heat loss of the fluid as a heatmedium can be reduced.

As the invention of claim 9 employs the above-mentioned ninth means,with respect to both of the fluid of high temperature and the fluid oflow temperature, the temperature of the most part of the supply pipingsand return pipings can be maintained constant. Thus, in addition to theeffect of the invention of claim 8, the heat loss becomes less and therecovery effect of the fluid or heat medium becomes large. Also,frequent starts and stops of the pumps are not needed so that theoperation becomes smooth and the mechanical durability is enhanced.

As the invention of claim 10 employs the above-mentioned tenth means, inaddition to the effect of the invention of claim 8 or 9, the pressure ofthe piping system can be maintained higher and the temperature of thefluid can be controlled in a higher temperature (150 to 160° C.) that isneeded by the mold.

As the invention of claim 11 or 12 employs the above-mentioned eleventhor twelfth means, at the time of heating the mold, the supply of thefluid of high temperature into the mold is stopped when the detectedmold temperature T is elevated to the high temperature fluid stoptemperature TH−ΔTH obtained by subtracting the heating over-shootingtemperature correction value ΔTH from the predetermined resin fillingstart temperature value TH. Also, at the time of cooling the mold, thesupply of the fluid of low temperature into the mold is stopped when thedetected mold temperature T is lowered to the low temperature fluid stoptemperature TL+ΔTL obtained by adding the cooling under-shootingtemperature correction value ΔTL to the predetermined mold opening starttemperature TL. Thus, the over-shooting or under-shooting of the moldtemperature is suppressed to the minimum and the molding cycle time canbe shortened.

According to the inventions of claims 13 to 27, at the time of heatingthe mold, the supply of the high temperature heat medium into the moldis stopped when the mold temperature is elevated to the high temperaturefluid stop temperature TH−ΔTH obtained by subtracting the heatingover-shooting temperature correction value ΔTH from the predeterminedresin filling start temperature value TH. Also, at the time of coolingthe mold, the supply of the low temperature heat medium into the mold isstopped when the mold temperature is lowered to the low temperaturefluid stop temperature TL+ΔTL obtained by adding the coolingunder-shooting temperature correction value ΔTL to the predeterminedmold opening start temperature TL. Thus, the over-shooting orunder-shooting of the mold temperature is not substantially caused andthe molding cycle time can be shortened.

Also, according to the present inventions, the heating over-shootingtemperature correction value ΔTH is predicted based on the time constantof the actually measured temperature changes when the mold as a singleunit is heated. Also, the cooling under-shooting temperature correctionvalue ΔTL is predicted based on the time constant of the actuallymeasured temperature changes when the mold as a single unit is cooled.Hence, the heating over-shooting temperature correction value ΔTH andcooling under-shooting temperature correction value ΔTL can be optimallyset.

Further, according to the inventions of claims 17, 18, 20 and 26, thetemperature control condition setting means for setting the moldtemperature control conditions is provided in the injection moldingcondition setting and displaying means provided on the molding machinecontrol means that controls the injection molding machine. The moldtemperature control conditions set by this temperature control conditionsetting means and the actually measured values of the mold in the actualmolding step are displayed on the injection molding condition settingand displaying means. Hence, to separately provide a temperature controlcondition setting means and a displaying means on the mold control unitis not necessary. Thus, the cost of the apparatus can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic piping diagram of a mold temperature adjustingapparatus of a molding machine of a first embodiment according to thepresent invention.

FIG. 2 is a partially cross sectional side view showing a first exampleof a concrete construction of a heat recovery tank of the moldtemperature adjusting apparatus of the first embodiment of FIG. 1.

FIG. 3 is a cross sectional view taken on line A-A of FIG. 2.

FIG. 4 is an enlarged partial side view showing a hole arrangement of amulti-hole plate of the heat recovery tank of FIG. 2.

FIG. 5 is a cross sectional side view showing a second example of theconcrete construction of the heat recovery tank of the mold temperatureadjusting apparatus of the first embodiment of FIG. 1.

FIG. 6 is a view showing one example of a cross sectional view taken online B-B of FIG. 5.

FIG. 7 is a view showing another example of the cross sectional viewtaken on line B-B of FIG. 5.

FIG. 8 is a cross sectional side view showing a third example of theconcrete construction of the heat recovery tank of the mold temperatureadjusting apparatus of the first embodiment of FIG. 1.

FIG. 9 is a view showing a circulation flow of high temperature water ina mold heating step of the mold temperature adjusting apparatus of thefirst embodiment.

FIG. 10 is a view showing flows of high temperature water and lowtemperature water in a high temperature water/low temperature waterchange-over high temperature water recovery step of the mold temperatureadjusting apparatus of the first embodiment.

FIG. 11 is a view showing a circulation flow of low temperature water ina mold cooling step of the mold temperature adjusting apparatus of thefirst embodiment.

FIG. 12 is a view showing flows of high temperature water and lowtemperature water in a low temperature water/high temperature waterchange-over low temperature water recovery step of the mold temperatureadjusting apparatus of the first embodiment.

FIG. 13 is a block diagram showing a heat medium behavior andheating/cooling timing represented on a time axis of molding steps whilemolding is carried out by change-over of mold temperature in the moldtemperature adjusting apparatus of the first embodiment mounted on amolding machine.

FIG. 14 is a schematic piping diagram of a mold temperature adjustingapparatus of a molding machine of a second embodiment according to thepresent invention, including a cross sectional view of a mold portion ofan injection molding machine.

FIG. 15 is a block diagram showing a temperature adjusting controlsystem of the mold temperature adjusting apparatus of the secondembodiment of FIG. 14.

FIG. 16 is a view showing one example of an image having writing-inframes of mold temperature set values and actually measured mold valuesfor each of operating steps of the injection molding machine.

FIG. 17 is a view showing one example of an image having an actuallymeasured wave shape of mold temperature changes when the mold is heatedand cooled by the mold temperature adjusting apparatus of the secondembodiment.

FIG. 18 is a schematic piping diagram of a mold temperature adjustingapparatus of a molding machine of a third embodiment according to thepresent invention, including a cross sectional view of a mold portion ofan injection molding machine.

FIG. 19 is a block diagram showing a temperature adjusting controlsystem of the mold temperature adjusting apparatus of the thirdembodiment of FIG. 17.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Herebelow, embodiments according to the present invention will bedescribed with reference to appended drawings.

First Embodiment

FIG. 1 is a schematic piping diagram of a mold temperature adjustingapparatus of a molding machine of a first embodiment according to thepresent invention, FIG. 2 is a partially cross sectional side viewshowing a first example of a concrete construction of a heat recoverytank of the mold temperature adjusting apparatus of the present firstembodiment, FIG. 3 is a cross sectional view taken on line A-A of FIG. 2and FIG. 4 is an enlarged partial view showing a hole arrangement of amulti-hole plate of the heat recovery tank of FIG. 2.

FIG. 5 is a cross sectional side view showing a second example of theconcrete construction of the heat recovery tank of the mold temperatureadjusting apparatus of the present first embodiment, FIG. 6 is a viewshowing one example of a cross sectional view taken on line B-B of FIG.5 and FIG. 7 is a view showing another example of the cross sectionalview taken on line B-B of FIG. 5.

FIG. 8 is a cross sectional side view showing a third example of theconcrete construction of the heat recovery tank of the mold temperatureadjusting apparatus of the present first embodiment.

The mold temperature adjusting apparatus of the first embodimentaccording to the present invention will be first described withreference to FIG. 1. In FIG. 1, the mold temperature adjusting apparatus1 comprises a mold 2 having a mold temperature sensor 62 fitted theretofor detecting temperature of the mold 2. Also, the mold 2 has a moldoutlet water temperature sensor 65 fitted to a heat medium outlet of themold 2 for detecting water temperature at the outlet of the mold 2.Further, the mold 2 has a fluid passage formed in the mold 2 or fittedto the mold 2.

Incidentally, as will be described also with respect to the secondembodiment, a mold of an injection molding machine is basicallyconstructed such that a fixed mold and a movable mold are closedtogether to form a mold cavity, a molten resin is injected into the moldcavity from an injection unit and then, after a molded article is cooledto solidify, the fixed mold and movable mold are separated from eachother so that the molded article is taken out. However, as thedescription of the mold temperature adjusting apparatus (means) of FIG.1 is mainly made on the aspect of the mold temperature adjustment,illustration of the injection unit is omitted in FIG. 1. Also, the mold2 shown in FIG. 1 represents a mold in the state that the fixed mold andmovable mold are closed together.

As shown in FIG. 1, the mold temperature adjusting apparatus (means) 1is constructed comprising a low temperature water tank (low temperaturefluid tank) 3, a high temperature water tank (high temperature fluidtank) 4, a heat recovery tank 5 (15, 25), a low temperature watertransfer pump (low temperature fluid transfer pump) 6, a low temperaturewater transfer pump (low temperature fluid transfer pump) 7 forelevating pressure, a high temperature water transfer pump (hightemperature fluid transfer pump) 8 and various pipings and valvesconnecting these parts and components.

The mold 2 is controlled by a molding machine control unit 115 to bedescribed with respect to FIG. 13 and the mold temperature adjustingapparatus 1 is controlled by a mold temperature control unit 132 to belikewise described with respect to FIG. 13.

While the low temperature water tank 3 can be constructed in an opentype, if the temperature of the high temperature water is to be 100° C.or more, the high temperature water tank 4 and heat recovery tank 5 (15,25) are constructed to be of a closed pressure type.

It is to be noted that when each of molding steps, describedhereinbelow, is changed over from one step to the other, the valves areopened or closed in unison or the valves to be opened are first openedand then the valves to be closed are closed.

In the low temperature water tank 3, in order to adjust the temperatureof the low temperature water to a set low temperature, a low temperaturewater temperature sensor 63 and a low temperature water temperatureadjuster (adjusting means) 32 are provided. Thereby, water temperaturein the low temperature water tank 3 is detected by the low temperaturewater temperature sensor 63 provided in the low temperature water tank 3and flow rate of a cooling medium flowing through the low temperaturewater temperature adjuster 32 is controlled by the mold temperaturecontrol unit 132 of FIG. 13 so that water temperature in the lowtemperature water tank 3 is maintained to a low temperature watertemperature set value TLW.

The low temperature water tank 3 and mold 2 are connected to each othervia a low temperature water supply system (low temperature fluid supplysystem) 31. That is, a low temperature water supply piping 31 a at itsone end is connected to a lower portion of the low temperature watertank 3. The low temperature water supply piping 31 a at the other end isconnected to a suction port of the low temperature water transfer pump6. The low temperature water transfer pump 6 elevates a dischargepressure of the low temperature water to 0.8 MPa and also has a functionof a check valve.

A low temperature water supply piping 31 b at its one end is connectedto a discharge port of the low temperature water transfer pump 6 and atthe other end is connected to a suction port of the low temperaturewater transfer pump 7. The low temperature water transfer pump 7elevates the discharge pressure of the low temperature water to 1.2 MPa.

A low temperature water supply piping 31 c elongates from a dischargeport of the low temperature water transfer pump 7 to connect to a lowtemperature water supply opening/closing valve 52 and a low temperaturewater supply piping 31 d elongates from the low temperature water supplyopening/closing valve 52 to connect to a heat medium inlet of the mold2.

Also, the mold 2 and low temperature water tank 3 are connected to eachother via a low temperature water return system (low temperature fluidreturn system) 35. That is, a low temperature water return piping 35 aat its one end is connected to the heat medium outlet of the mold 2 andat the other end is connected to a low temperature water returnopening/closing valve 55. A low temperature water return piping 35 belongates from the low temperature water return opening/closing valve 55to connect to an upper portion of the low temperature water tank 3.

The low temperature water supply piping 31 c and low temperature waterreturn piping 35 b are connected to each other via a low temperaturewater by-pass system (low temperature fluid by-pass system) 40. This lowtemperature water by-pass system 40 comprises a low temperature waterby-pass piping 34 and a low temperature water by-pass opening/closingvalve 51 interposed in the low temperature water by-pass piping 34.

In the high temperature water tank 4, in order to adjust the temperatureof the high temperature water to a set high temperature, a hightemperature water temperature sensor 64 and a high temperature watertemperature adjuster (adjusting means) 33 are provided. Thereby, watertemperature in the high temperature water tank 4 is detected by the hightemperature water temperature sensor 64 provided in the high temperaturewater tank 4 and flow rate of a heating medium flowing through the hightemperature water temperature adjuster 33 is controlled by the moldtemperature control unit 132 so that water temperature in the hightemperature water tank 4 is maintained to a high temperature watertemperature set value THW.

The high temperature water tank 4 and mold 2 are connected to each othervia a high temperature water supply system (high temperature fluidsupply system) 41. That is, a lower portion of the high temperaturewater tank 4 is connected to a suction port of a high temperature watertransfer pump 8. A high temperature water supply piping 41 a elongatesfrom a discharge port of the high temperature water transfer pump 8 toconnect to a high temperature water supply opening/closing valve 53 anda high temperature water supply piping 41 b elongates from the hightemperature water supply opening/closing valve 53 to connect to the heatmedium inlet of the mold 2.

Also, the mold 2 and high temperature water tank 4 are connected to eachother via a high temperature water return system (high temperature fluidreturn system) 42. That is, a high temperature water return piping 42 aat its one end is connected to the heat medium outlet of the mold 2 andat the other end is connected to a high temperature water returnopening/closing valve 54. A high temperature water return piping 42 belongates from the high temperature water return opening/closing valve54 to connect to an upper portion of the high temperature water tank 4.

The high temperature water supply piping 41 a and high temperature waterreturn piping 42 b are connected to each other via a high temperaturewater by-pass system (high temperature fluid by-pass system) 43. Thishigh temperature water by-pass system 43 comprises a high temperaturewater by-pass piping 43 a and a high temperature water by-passopening/closing valve 56 interposed in the high temperature waterby-pass piping 43 a.

The high temperature water tank 4 and the low temperature water tank 3are connected to each other via a make-up piping 39 and a manualopening/closing valve 59 interposed in the make-up piping 39. Thismake-up piping 39 is provided for supplying or making up water into thehigh temperature water tank 4. It is to be noted that the make-up piping39 has also a supply pump, etc. interposed therein, althoughillustration is omitted.

By the construction mentioned above, in a molding step of a resin moldedarticle by an injection molding machine, the low temperature watersupply opening/closing valve 52 of the low temperature water supplysystem 31 and the low temperature water return opening/closing valve 55of the low temperature water return system 35 are closed and, at thesame time, the high temperature water supply opening/closing valve 53 ofthe high temperature water supply system 41 and the high temperaturewater return opening/closing valve 54 of the high temperature waterreturn system 42 are opened. Thereby, the high temperature water flowsin the heat medium passage of the mold 2 and the mold 2 can be heated.

Reversely to the above, the low temperature water supply opening/closingvalve 52 of the low temperature water supply system 31 and the lowtemperature water return opening/closing valve 55 of the low temperaturewater return system 35 are opened and, at the same time, the hightemperature water supply opening/closing valve 53 of the hightemperature water supply system 41 and the high temperature water returnopening/closing valve 54 of the high temperature water return system 42are closed. Thereby, the low temperature water flows in the heat mediumpassage of the mold 2 and the mold 2 can be cooled.

Also, by closing the low temperature water supply opening/closing valve52 and low temperature water return opening/closing valve 55 and, at thesame time, by opening the low temperature water by-pass opening/closingvalve 51 of the low temperature water by-pass system 40, the lowtemperature water can be circulated without the low temperature waterflowing through the mold 2.

Further, by closing the high temperature water supply opening/closingvalve 53 and high temperature water return opening/closing valve 54 and,at the same time, by opening the high temperature water by-passopening/closing valve 56 of the high temperature water by-pass system43, the high temperature water can be circulated without the hightemperature water flowing through the mold 2.

The heat recovery tank 5 (15, 25) is provided between the lowtemperature water tank 3 and the high temperature water tank 4. The heatrecovery tank 5 has a volume larger than the total of a volume of theheat medium passage in the mold 2 and volumes of the high temperaturewater supply pipings 41 a, 41 b and high temperature water returnpipings 42 a, 42 b of the high temperature heat medium. The heatrecovery tank 5 has its upper portion provided with a high temperaturewater inlet and its lower portion provided with a low temperature waterinlet. Also, the heat recovery tank 5 is a tank of a longitudinallyelongated cylindrical shape comprising therein a means suppressingmixing of the high temperature water and low temperature water containedin the tank, as will be described later.

The high temperature water inlet of the heat recovery tank 5 isconnected to the high temperature water tank 4 via a transfer piping 44.Also, the low temperature water inlet of the heat recovery tank 5 isconnected to the low temperature water supply piping 31 b between thelow temperature water transfer pump 6 and the low temperature watertransfer pump 7 via a feed side piping 36 and an opening/closing pump 57interposed in the feed side piping 36.

A pressure adjusting system 37 comprises return pipings 37 a, 37 b. Thereturn piping 37 a at its one end is connected to the feed side piping36 between the opening/closing valve 57 and the heat recovery tank 5 andat the other end is connected with a low temperature water pressureadjusting valve 61. The return piping 37 b elongates from a lowerportion of the low temperature water tank 3 to connect to the lowtemperature water pressure adjusting valve 61. An opening/closing valve58 is interposed in the return piping 37 a. The low temperature waterpressure adjusting valve 61 functions to constantly maintain waterpressure on the heat recovery tank 5 side.

Next, a first example of a concrete construction of the heat recoverytank 5 will be described with reference to FIGS. 2 to 4. As shown inFIGS. 2 and 3, the heat recovery tank 5 is constructed by an upper cover11, a lower cover 12 and a main body portion between the upper and lowercovers 11, 12. The main body portion comprises a central cylinder 5 a ofa circular cross sectional cylindrical shape and upper and lowercylinder portions 5 b, 5 c both being integrally formed with the centralcylinder 5 a and having a diameter slightly larger than that of thecentral cylinder 5 a. It is to be noted that numeral 14 in FIG. 2designates an air vent screw screwed in the upper cover 11.

In each of the upper and lower cylinder portions 5 b, 5 c, a multi-holeplate 13 formed in a circular cross sectional cylindrical shape having adiameter approximately the same as that of the central cylinder 5 a isprovided substantially coaxially with the central cylinder 5 a. As shownin FIG. 4, the multi-hole plate 13 has multi-holes 13 a, each having adiameter dl, regularly bored therein.

The upper cylinder portion 5 b has a water pipe 5 d, integrally formedwith the upper cylinder portion 5 b, through which the high temperaturewater horizontally flows in or flows out along an inner circumferentialsurface of the upper cylinder portion 5 b. Likewise, the lower cylinderportion 5 c has a water pipe 5 e, integrally formed with the lowercylinder portion 5 c, through which the low temperature waterhorizontally flows in or flows out along an inner circumferentialsurface of the lower cylinder portion 5 c. The water pipe 5 d of theupper cylinder portion 5 b is connected to the transfer piping 44. Thewater pipe 5 e of the lower cylinder portion 5 c is connected to thefeed side piping 36.

A heat insulating material 46 is applied to or coated on an innersurface of the central cylinder 5 a. A longitudinal length or height ofthis heat insulating material 46 is slightly larger than a distance orheight h between an upper limit L_(H) and a lower limit L_(L) of aboundary surface between the high temperature water and the lowtemperature water, as will be described later.

Thus, both on the low temperature water side and the high temperaturewater side, the inlet and outlet of the heat medium water arehorizontally provided along the inner circumferential surfaces of theupper and lower cylinder portions 5 b, 5 c, so that a longitudinaldynamic pressure of the heat medium water at the time when the heatmedium water is fed from the respective inlets is reduced. Also, themulti-hole plate 13 is provided in each of the upper and lower cylinderportions 5 b, 5 c so that a flow resistance of the heat medium water iscaused to thereby make a flow velocity of the heat medium water uniformin the heat recovery tank 5. As the result thereof, a convection of theheat medium water in the heat recovery tank 5 is reduced. Hence, in theheat recovery tank 5, the low temperature water and high temperaturewater are prevented from mixing with each other and the boundary betweenthe low temperature water and the high temperature water can bemaintained by the specific gravity difference.

There is known a theoretical equation to ascertain a non-uniformity ofthe heat medium boundary by the specific gravity difference. That is,where dl is a diameter of the hole 13 a of the multi-hole plate 13 andvl is a flow velocity of the heat medium entering the central cylinder 5a through the hole 13 a, dimensions of the heat recovery tank 5 aredesigned so that Ri, given by the following equation, becomes 10 ormore:Ri=Δρ·g·dl/(ρmean·v1 ²)

-   -   Here, g: Gravitational acceleration    -   Δρ: Density difference between the low temperature medium and        the high temperature medium    -   ρ mean: Mean density of the heat medium

Ri number is a non-dimensional number representing a ratio of thebuoyancy term to the inertia term. The larger is the value of Ri, themore easily tends a thermal stratification to be generated andstabilized. Hence, a heat transmission between the high temperaturemedium (water) and the low temperature medium (water) due to theirregular flow can be suppressed.

When the high temperature water and low temperature water are to berecovered by using the heat recovery tank 5, the boundary surfacebetween the high temperature water and the low temperature water movesin the distance or height h between the upper limit L_(H) and the lowerlimit L_(L), as shown in FIG. 2. Hence, by multiplying an inner diametercross sectional area of the central cylinder 5 a by the height h, arecovery volume of the high temperature water or low temperature watercan be obtained. The heat insulating material 46 has a small thermalcapacity and a large heat insulating ability. Hence, the hightemperature water is deprived of less heat quantity and the heat losscan be reduced.

A second example of the concrete construction of the heat recovery tankwill be described with reference to FIGS. 5 to 7. As shown in FIG. 5, aheat recovery tank 15 is constructed by an upper cover 11, lower cover12 and tank main body 16 between the upper and lower covers 11, 12. Thetank main body 16 comprises a central cylinder 16 a of a circular crosssectional cylindrical shape and upper and lower cylinder portions 16 b,16 c both being integrally formed with the central cylinder 16 a andhaving a diameter slightly larger than that of the central cylinder 16a. It is to be noted that numeral 14 in FIG. 5 designates an air ventscrew screwed in the upper cover 11. Also, the heat recovery tank 15 isnot limited to the circular cross sectional cylindrical shape but may beformed in a length-wise elongated cylindrical shape having a polygonalcross section including a square or rectangular cross section.

In each of the upper and lower cylinder portions 16 b, 16 c, amulti-hole plate 17 formed in a flat disc shape is horizontally fittedto an inner periphery of the respective cylinder portions 16 b, 16 c.Like the multi-hole plate 13 shown in FIG. 4, the multi-hole plate 17has multi-holes 17 a, each having a diameter dl, regularly boredtherein.

The upper cylinder portion 16 b has a water pipe 16 d, integrally formedwith the upper cylinder portion 16 b, through which the high temperaturewater horizontally flows in or flows out along an inner circumferentialsurface of the upper cylinder portion 16 b. Likewise, the lower cylinderportion 16 c has a water pipe 16 e, integrally formed with the lowercylinder portion 16 c, through which the low temperature waterhorizontally flows in or flows out along an inner circumferentialsurface of the lower cylinder portion 16 c. The water pipe 16 d of theupper cylinder portion 16 b is connected to the transfer piping 44. Thewater pipe 16 e of the lower cylinder portion 16 c is connected to thefeed side piping 36.

A plurality of longitudinally elongating flat plate shaped rectifyingplates 18 are provided in the central cylinder 16 a along an axialdirection thereof. These rectifying plates 18 are arranged in parallelto each other with a constant gap being maintained between each of themand have their upper and lower portions supported by support bars 18 afitted to upper and lower portions, respectively, of the centralcylinder 16 a.

Thus, both on the low temperature water side and high temperature waterside, the inlet and outlet of the heat medium water are horizontallyprovided along the inner circumferential surfaces of the upper and lowercylinder portions 16 b, 16 c, so that a longitudinal dynamic pressure ofthe heat medium water at the time when the heat medium water is fed fromthe respective inlets is reduced. Also, the multi-hole plate 17 isprovided between the upper cylinder portion 16 b and the centralcylinder 16 a and between the central cylinder 16 a and the lowercylinder portion 16 c, respectively, so that a flow resistance of theheat medium water is caused to thereby make a flow velocity of the heatmedium water uniform in the heat recovery tank 15. Moreover, the flow ofthe heat medium water is rectified by the rectifying plates 18. As theresult thereof, a convection of the heat medium water in the heatrecovery tank 15 is reduced. Hence, in the heat recovery tank 15, thelow temperature water and high temperature water are prevented frommixing with each other and the boundary between the low temperaturewater and the high temperature water can be maintained by the specificgravity difference.

In order to reduce a thermal loss, the rectifying plates 18 arepreferably constructed by plates or the like of a heat insulatingmaterial having a heat resistant nature.

It is to be noted that, in place of the above-mentioned flat plateshaped rectifying plates 18 provided in the central cylinder 16 a, aplurality of corrugated rectifying plates 19, arranged with a constantgap being maintained between each of them and supported by support bars19 a, as shown in FIG. 7, may be used.

A third example of the concrete construction of the heat recovery tankwill be described with reference to FIG. 8. In FIG. 8, the parts andcomponents same as those of the second example of the concreteconstruction of the heat recovery tank are given with the same referencenumerals with description thereof being omitted and different pointswill be described.

In the present third example of the concrete construction of the heatrecovery tank, in place of the rectifying plates 18 of the heat recoverytank 15 shown in FIG. 5, a float disc 27 is provided in a centralcylinder 16 a of a heat recovery tank 25, as shown in FIG. 8. This floatdisc 27 has a specific gravity of an intermediate value between aspecific gravity of the high temperature water and that of the lowtemperature water so that the float disc 27 floats in the boundarybetween the high temperature water and the low temperature water.Thereby, the high temperature water and low temperature water areprevented from mixing with each other.

In the heat recovery tank 25, a guide-bar 26 is perpendicularly providedhaving its one end fixed to a central position of a lower cover 12 ofthe heat recovery tank 25, so that the float disc 27, having an outerdiameter slightly smaller than an inner diameter of the central cylinder16 a, is guided by the guide bar 26 so as to move up and down along theguide bar 26. The float disc 27 is made of a heat insulating material.The float disc 27 has its central portion provided with a guide pipe,having an appropriate length in the perpendicular direction, in whichthe guide bar 26 is loosely inserted. Numeral 28 designates a rectifierof an arbitrary type.

In the construction mentioned above, if the temperature of the hightemperature water is set to 100° C., its specific gravity is about 0.94and if the temperature of the low temperature water is set to 20° C.,its specific gravity is about 1.00. Hence, if the overall specificgravity of the float disc 27 is set to 0.97, when the high temperaturewater and low temperature water are fed into the upper portion and lowerportion, respectively, of the heat recovery tank 25, the float disc 27floats in the boundary therebetween so as to function as a separatingmeans of the high temperature water and low temperature water from eachother.

In place of the float disc 27 made of the heat insulating material, adisc shape bag, made of a soft material and filled with water, can beused. In this case, water temperature in the disc shape bag becomesintermediate between the temperature of the high temperature water andthat of the low temperature water and hence the specific gravity of thewater in the bag becomes intermediate between the specific gravity ofthe high temperature water and that of the low temperature water.

Next, function of the mold temperature adjusting apparatus 1 and controlcontents of the molding machine control unit 115 and mold temperaturecontrol unit 132 will be described with reference to FIGS. 9 to 13.

FIG. 9 is a view showing a circulation flow of the high temperaturewater in a mold heating step of the mold temperature adjusting apparatusof the present first embodiment. FIG. 10 is a view showing flows of thehigh temperature water and low temperature water in a high temperaturewater/low temperature water change-over high temperature water recoverystep. FIG. 11 is a view showing a circulation flow of the lowtemperature water in a mold cooling step. FIG. 12 is a view showingflows of the high temperature water and low temperature water in a lowtemperature water/high temperature water change-over low temperaturewater recovery step.

FIG. 13 is a block diagram showing a heat medium behavior andheating/cooling timing represented on a time axis of molding steps whilemolding is carried out by change-over of temperature of the mold 2 inthe mold temperature adjusting apparatus of the present first embodimentmounted on a molding machine. That is, in FIG. 13, the top portionthereof shows control contents of the molding machine control unit 115,a curved line of the upper mid portion shows a changing state oftemperature and a lower portion shows control contents of the moldtemperature control unit 132.

As shown in FIG. 13, in injection molding steps to heat the mold 2before filling a molten resin and to cool the mold 2 after filling themolten resin in an injection molding machine, the mold 2 is heated orcooled in a high temperature water circulation (mold heating) step, alow temperature water circulation (molding cooling) step, a hightemperature water recovery (mold cooling) step and a low temperaturewater recovery (mold heating) step, all to be described later.

In the mold temperature control unit 132, there are previously set aheating over-shooting temperature correction value ΔTH at the time whenthe mold 2 is to be heated, a cooling under-shooting temperaturecorrection value ΔTL at the time when the mold 2 is to be cooled, aresin filling start mold temperature TH of the high temperature mold 2at the time when a filling step is to be started, a cooling finishtemperature (hereinafter sometimes referred to as “a mold opening starttemperature”) TL, an over-shooting time (hereinafter sometimes referredto as “a high temperature water by-passing action set time”) S1, anunder-shooting time (hereinafter sometimes referred to as “a lowtemperature water by-passing action set time”) S2, a feed time(hereinafter sometimes referred to as “a high temperature water recoverytime set value”) S3 and a feed time (hereinafter sometimes referred toas “a low temperature water recovery time set value”) S4.

Here, as a heat transmission velocity is slow when a member having alarge thermal capacity, like the mold 2, is heated, the heatingover-shooting temperature correction value ΔTH at the heating time meansa set value (correction value) of temperature that is still elevatedeven if feed of the heat medium is stopped at the set temperature.Reversely, the cooling under-shooting temperature correction value ΔTLat the cooling time means a set value (correction value) of temperaturethat is still lowered even if feed of the cooling medium is stopped atthe set temperature.

It is to be noted that while a recovery of the low temperature water inthe second and third embodiments, to be described later, is startedbefore the mold opening start temperature TL is realized, the recoveryof the low temperature water in the present first embodiment is startedafter the mold opening start temperature TL has been realized.Thereafter, a high temperature fluid stop temperature TH−ΔTH iscalculated by subtracting the heating over-shooting temperaturecorrection value ΔTH from the resin filling start mold temperature THand a low temperature fluid stop temperature TL+ΔTL is calculated byadding the cooling under-shooting temperature correction value ΔTL tothe mold opening start temperature TL.

(1-1) High Temperature Water Circulation Step as Part of the MoldHeating Step

In the high temperature water circulation step as a middle part of themold heating step shown in FIG. 13, the mold temperature control unit132 performs a control such that, as shown in FIG. 9, the lowtemperature water supply opening/closing valve 52 of the low temperaturewater supply system 31 and the low temperature water returnopening/closing valve 55 of the low temperature water return system 35are closed and the low temperature water by-pass opening/closing valve51 of the low temperature water by-pass system 40 is opened.

Further, on the high temperature water side, the high temperature waterby-pass opening/closing valve 56 of the high temperature water by-passsystem 43 is closed and the high temperature water supplyopening/closing valve 53 of the high temperature water supply system 41and the high temperature water return opening/closing valve 54 of thehigh temperature water return system 42 are opened.

The low temperature water transfer pump 6, the low temperature watertransfer pump 7 for elevating pressure and the high temperature watertransfer pump 8 are continuously operated throughout the hightemperature water circulation step and subsequent steps thereof.

By the operation mentioned above, flow of the low temperature water isreturned into the low temperature water tank 3 via the low temperaturewater by-pass piping 34 without being supplied into the mold 2.

On the other hand, by the high temperature water transfer pump 8, thehigh temperature water is supplied into the mold 2 via the hightemperature water supply system 41 and is returned through the hightemperature water return system 42 and thereby the mold 2 is heated.

While the mold 2 is being so heated, the mold 2 is closed by the moldingmachine control unit 115 on the injection molding machine side, as shownin FIG. 13.

By the high temperature water being supplied into the mold 2, quantityof the high temperature water in the high temperature water tank 4 isreduced. On the other hand, the opening/closing valve 57 interposed inthe feed side piping 36 is opened and the opening/closing valve 58interposed in the pressure adjusting system 37 is closed.

Thus, corresponding to the reduced quantity of the high temperaturewater, the low temperature water transfer pump 6 is operated so that thelow temperature water is supplied into the lower portion of the heatrecovery tank 5 via the feed side piping 36 and the high temperaturewater in the upper portion of the heat recovery tank 5 is transferredinto the high temperature water tank 4 via the transfer piping 44.

(1-2) High Temperature Water By-Passing Step as Part of the Mold HeatingStep

In the high temperature water by-passing step as a latter part of themold heating step shown in FIG. 13, when a mold temperature T detectedby the mold temperature sensor 62 reaches the high temperature fluidstop temperature TH−ΔTH, the high temperature water supplyopening/closing valve 53 of the high temperature water supply system 41and the high temperature water return opening/closing valve 54 of thehigh temperature water return system 42 are closed to thereby stop thehigh temperature water to be supplied into the mold 2. Also, the hightemperature water by-pass opening/closing valve 56 is opened to therebycause the high temperature water to by-pass through the high temperaturewater by-pass system 43. Thus, the high temperature water returns intothe high temperature water tank 4.

Also, the low temperature water returns into the low temperature watertank 3 via the low temperature water by-pass system 40.

In the meanwhile, the injection molding machine side is on a stand-bystate for injection and filling, as shown in FIG. 13.

(2-1) High Temperature Water Recovery Step as Part of the Mold CoolingStep

When a high temperature water by-pass timer TM1 in the mold temperaturecontrol unit 132 judges that the high temperature water by-passingaction set time S1 has passed, in the high temperature water recoverystep as a former part of the mold cooling step shown in FIG. 13, thehigh temperature water return opening/closing valve 54 of the hightemperature water return system 42 is closed, as shown in FIG. 10. Atthe same time, the low temperature water by-pass opening/closing valve51 of the low temperature water by-pass system 40 is closed and the lowtemperature water supply opening/closing valve 52 of the low temperaturewater supply system 31 is opened.

By the operation mentioned above, the low temperature water is suppliedinto the heat medium water passage of the mold 2 and thereby the hightemperature water remaining in the mold 2 and surrounding pipingsthereof is pushed out to flow through the high temperature water returnsystem 42 and is recovered into the high temperature water tank 4 andfurther into the heat recovery tank 5.

The high temperature water entering the upper portion of the heatrecovery tank 5 from the high temperature water tank 4 is prevented frommixing with the low temperature water by a means suppressing mixing ofthe high temperature water and low temperature water, such as by agravity separation, and is stored in the upper portion of the heatrecovery tank 5.

At this time, the opening/closing valve 57 interposed in the feed sidepiping 36 is closed and the opening/closing valve 58 interposed in thepressure adjusting system 37 is opened. Thus, when the total quantity ofthe high temperature water and low temperature water in the heatrecovery tank 5 exceeds a capacity of the heat recovery tank 5, the lowtemperature water in the lower portion of the heat recovery tank 5 flowsout to be fed into the low temperature water tank 3 via the feed sidepiping 36 and pressure adjusting system 37.

The high temperature water recovery time set value S3 can be previouslyobtained from the relation between a recovery quantity of the hightemperature water (high temperature water remaining quantity) remainingin the mold 2 and surrounding pipings thereof and a feed quantity of thelow temperature water transfer pump 7.

When a high temperature water recovery timer TM3 in the mold temperaturecontrol unit 132 judges that the high temperature water recovery timeset value S3 has passed, the high temperature water returnopening/closing valve 54 of the high temperature water return system 42is closed to thereby finish the recovery of the high temperature waterand, at the same time, the low temperature water return opening/closingvalve 55 is opened, as will be described later.

It is to be noted that in place of setting and using the hightemperature water recovery time set value S3, a change-over temperatureof the heat medium water temperature at the heat medium water outlet ofthe mold 2 is set in the mold temperature control unit 132 and when thetemperature detected by the mold outlet water temperature sensor 65exceeds this set value, the high temperature water returnopening/closing valve 54 may be operated to be closed.

While the high temperature water return opening/closing valve 54 is soclosed, the high temperature water returns into the high temperaturewater tank 4 via the high temperature water by-pass system 43.

Also, on the injection molding machine side, when the detected moldtemperature T reaches the resin filling start mold temperature TH, aninjection and filling step is started, as shown in FIG. 13.

(2-2) Low Temperature Water Circulation Step as Part of the Mold CoolingStep

In the low temperature water circulation step as a middle part of themold cooling step shown in FIG. 13, after the high temperature water hasbeen recovered into the heat recovery tank 5 from the mold 2, the lowtemperature water return opening/closing valve 55 of the low temperaturewater return system 35 is opened, as shown in FIG. 11. By thisoperation, the low temperature water is supplied into the mold 2 so thatthe mold cooling step of the mold 2 is continued.

On the high temperature water side, the high temperature water supplyopening/closing valve 53 of the high temperature water supply system 41and the high temperature water return opening/closing valve 54 of thehigh temperature water return system 42 are closed. Also, the hightemperature water by-pass opening/closing valve 56 is opened. Thereby,the supply of the high temperature water into the mold 2 is stopped andthe high temperature water is caused to by-pass through the hightemperature water by-pass system 43. Thus, the high temperature water iscirculated between the high temperature water by-pass system 43 and thehigh temperature water tank 4.

At this time, the opening/closing valve 57 interposed in the feed sidepiping 36 is opened and the opening/closing valve 58 interposed in thepressure adjusting system 37 is closed. Thus, pressure in the heatrecovery tank 5 and high temperature water tank 4 is elevated by the lowtemperature water transfer pump 6.

On the injection molding machine side, an injected resin pressuremaintaining and mold cooling step is commenced.

(2-3) Low Temperature Water By-Passing Step as Part of the Mold CoolingStep

In the low temperature water by-passing step as a latter part of themold cooling step shown in FIG. 13, when the detected mold temperature Treaches the low temperature fluid stop temperature TL+ΔTL, the lowtemperature water by-pass opening/closing valve 51 of the lowtemperature water by-pass system 40 is opened and the low temperaturewater supply opening/closing valve 52 of the low temperature watersupply system 31 and the low temperature water return opening/closingvalve 55 of the low temperature water return system 35 are closed.

By this operation, the supply of the low temperature water into the mold2 is stopped and the low temperature water returns into the lowtemperature water tank 3 via the low temperature water by-pass system 40and low temperature water return system 35.

(3-1) Low Temperature Water Recovery Step as Part of the Mold HeatingStep

When a low temperature water by-pass timer TM2 in the mold temperaturecontrol unit 132 judges that the low temperature water by-passing actionset time S2 has passed, in the low temperature water recovery step as aformer part of the mold heating step shown in FIG. 13, the lowtemperature water return opening/closing valve 55 of the low temperaturewater return system 35 is opened, as shown in FIG. 12. At the same time,the high temperature water by-pass opening/closing valve 56 of the hightemperature water by-pass system 43 is closed and the high temperaturewater supply opening/closing valve 53 of the high temperature watersupply system 41 is opened.

The low temperature water is fed into the lower portion of the heatrecovery tank 5 by hydraulic pressure given by the low temperature watertransfer pump 6 to be replaced with the high temperature water there.Thereby, the high temperature water in the upper portion of the heatrecovery tank 5 is fed into the high temperature water tank 4 and thelow temperature water remaining in the mold 2 and surrounding pipingsthereof is recovered into the low temperature water tank 3.

The low temperature water recovery time set value S4 can be previouslyobtained from the relation between a recovery quantity of the lowtemperature water (low temperature water remaining quantity) remainingin the mold 2 and surrounding pipings thereof and a feed quantity of thehigh temperature water transfer pump 8.

When a low temperature water recovery timer TM4 in the mold temperaturecontrol unit 132 judges that the low temperature water recovery time setvalue S4 has passed, the high temperature water return opening/closingvalve 54 is opened and the low temperature water return opening/closingvalve 55 of the low temperature water return system 35 is closed tothereby finish the recovery of the low temperature water.

It is to be noted that in place of setting and using the low temperaturewater recovery time set value S4, a change-over temperature of the heatmedium water temperature at the heat medium water outlet of the mold 2is set in the mold temperature control unit 132 and when the temperaturedetected by the mold outlet water temperature sensor 65 exceeds this setvalue, the high temperature water return opening/closing valve 54 may beoperated to be opened and the low temperature water returnopening/closing valve 55 may be operated to be closed.

(3-2) High Temperature Water Circulation Step as Part of the MoldHeating Step

After the low temperature water recovery time set value S4 detected bythe low temperature water recovery timer TM4 has passed, in the hightemperature water circulation step as a middle part of the mold heatingstep shown in FIG. 13, the low temperature water return opening/closingvalve 55 of the low temperature water return system 35 is kept closedand the high temperature water return opening/closing valve 54 of thehigh temperature water return system 42 is kept opened. Thus, after thelow temperature water is recovered to be replaced with the hightemperature water, the low temperature water is circulated through theby-pass passage and the high temperature water is continuously suppliedinto the mold 2 so that the high temperature water circulation step inthe mold heating step, as mentioned above, is again commenced.

On the injection molding machine side, when the detected moldtemperature T reaches the mold opening start temperature TL, the moldcooling step of the mold 2 is completed. Then, the mold 2 is opened sothat the molded article is taken out. Subsequently, a mold closingstand-by step and the above-mentioned mold closing step are carried out.

As mentioned above, in the high temperature water recovery step in themold temperature adjusting step, the high temperature water in the mold2 and surrounding pipings thereof is recovered into the high temperaturewater tank 4 or into the heat recovery tank 5 by the low temperaturewater in the low temperature water supply system 31.

Further, in the low temperature water recovery step, the low temperaturewater in the mold 2 and surrounding pipings thereof is recovered intothe low temperature water tank 3 by the high temperature water in thehigh temperature water supply system 41.

At this time, the heat recovery tank 5 functions as a buffer of the hightemperature water tank 4 so that the high temperature water overflowingthe high temperature water tank 4 is primarily stored in the upperportion of the heat recovery tank 5.

Thus, as the high temperature water is in no case discharged outside,heat loss can be suppressed to the minimum. Also, as the low temperaturewater transfer pump 6, low temperature water transfer pump 7 forelevating pressure and high temperature water transfer pump 8 arecontinuously operated, mechanical and electrical shocks caused by startsand stops become less and the endurability is enhanced.

In the above-mentioned mold temperature adjusting step, by continuouslyoperating the low temperature water transfer pump 6 and by adjusting thelow temperature water pressure adjusting valve 61 provided in thepressure adjusting system 37 connected to the low temperature water tank3, interior of the high temperature water piping system is maintained ina higher pressure so that a vaporizing temperature of the hightemperature water is elevated and the mold 2 can be controlled in ahigher temperature.

In the injection step of the injection molding machine, if thetemperature of the mold 2 is low, there is a risk in the conventionalmachine that the molten resin making contact with the mold 2 quicklysolidifies before the pressure of the injected molten resin issufficiently elevated so that the surface of the molded article becomescoarse to thereby make a transfer of a cavity face of the mold 2insufficient. But according to the mold temperature adjusting apparatusof the present embodiment, the temperature of the mold 2 is maintainedhigher at the time of injection and filling so that solidification ofthe surface of the molten resin, after filled, is delayed and then themold 2 is forcibly cooled. Thus, the cycle of the injection step can beshortened.

Actual Example

The temperature adjustment according to the present invention is carriedout using ABS resin under the condition of the high temperature watertemperature of 150° C. and the low temperature water temperature of 20°C., wherein the resin filling start mold temperature TH is set to 120°C., the heating over-shooting temperature correction value ΔTH to 15°C., the mold opening start temperature TL to 70° C. and the coolingunder-shooting temperature correction value ΔTL to 20° C.

The result obtained shows that there is caused no substantialover-shooting of the temperature to thereby shorten the molding cycle to50 seconds from 70 seconds and the surface deterioration of the moldedarticle is solved to thereby enhance the transfer ability.

Second Embodiment

Next, a mold temperature adjusting apparatus of a second embodimentaccording to the present invention will be described with reference toFIGS. 14 to 17. Also, a mold temperature adjusting method with respectto this second embodiment will be described.

In the present second embodiment, as compared with the first embodimentas described above, there are provided neither the low temperature waterby-pass system 40 nor the high temperature water by-pass system 43, butthe heat medium is likewise controlled such that opening and closing ofeach of the valves are effected as well as start and stop of the hightemperature water transfer pump 8 are carried out. Nevertheless, theconstruction may also be made such that the low temperature waterby-pass system 40 and the high temperature water by-pass system 43 areprovided being connected to the mold temperature adjusting apparatus,like in the first embodiment, to thereby control the flow of the heatmedium by opening and closing each of the valves.

Further, as compared with the first embodiment, a hydraulic pressurechange-over valve 116, a molding machine control unit 115 and a moldtemperature control unit 112 are illustrated in FIG. 14 being connectedto the mold temperature adjusting apparatus 1′ of the present secondembodiment.

FIG. 14 is a schematic piping diagram of, including a cross sectionalview of a mold portion of an injection molding machine. FIG. 15 is ablock diagram showing a temperature adjusting control system of the moldtemperature adjusting apparatus of FIG. 14. FIG. 16 is a view showingone example of an image having writing-in frames of mold temperature setvalues and actually measured mold values for each of operating steps ofthe injection molding machine. FIG. 17 is a view showing one example ofan image having an actually measured wave shape of mold temperaturechanges when the mold is heated and cooled by the mold temperatureadjusting apparatus of FIG. 14.

Herebelow, additionally to the description of the mold temperatureadjusting apparatus of the first embodiment, a construction of a moldclosing apparatus 120 of the injection molding machine will be describedwith reference to FIG. 14. The parts and components substantially thesame as those of the first embodiment are designated with the samereference numerals and description thereof will be omitted.

The mold closing apparatus 120 comprises a fixed die plate 102 fixedlysupported to a base 101 and a movable die plate 103 opposedly providedto this fixed die plate 102. The movable die plate 103 is supported on aguide rail 113 provided on the base 101 so as to be movable to and fromthe fixed die plate 102 via linear bearings 118. For movement of themovable die plate 103, a die plate moving hydraulic cylinder 112effecting a hydraulic power drive is used as one example. The fixed dieplate 102 has its surface opposing the movable die plate 103 fitted witha fixed mold 104 and the movable die plate 103 has its surface opposingthe fixed die plate 102 fitted with a movable mold 105. The fixed mold104 and movable mold 105 constitute the mold 2. Thus, by the movement ofthe movable die plate 103 driven by the die plate moving hydrauliccylinder 112, opening and closing of the fixed mold 104 and movable mold105, or the mold 2, are effected.

In the fixed die plate 102, a plurality of mold closing hydrauliccylinders 102 a are provided. These mold closing hydraulic cylinders 102a are provided in four corner portions of the fixed die plate 102, forexample.

A ram 108 is slidably arranged in each of the mold closing hydrauliccylinders 102 a and a tie bar 109, having its distal end portionthreaded, is connected to the ram 108. The distal end portion of the tiebar 109 passes through the movable die plate 103 and is connected, via athread engagement, with half nuts 111 provided on the movable die plate103 on the reverse side of the mold opposing the fixed die plate 102.Thereby, the tie bar 109 can move together with the movable die plate103.

There is provided a hydraulic power change-over valve 116 controlled bya command given from the molding machine control unit 115 so that adrive hydraulic power of the mold closing hydraulic cylinders 102 a, aninjection screw 107 and the like is changed over. The molding machinecontrol unit 115 comprises a setting and displaying means 115 a havingan image displaying panel of touch key type. By this setting anddisplaying means 115 a, set values of the molding conditions of themolding machine, such as an injection pressure and the like, are set aswell as actually measured values of the injection pressure and the likeare displayed by an image of wave shape or the like.

An injection unit 110 is provided comprising an injection cylinder 106,the injection screw 107 and the like so that a molten resin is injectedinto a mold cavity formed in the mold when the fixed mold 104 andmovable mold 105 are closed and clamped together. The injection cylinder106 comprises a nozzle that abuts on a resin inlet of the fixed mold 104during the injection operation. The injection screw 107 is rotationallydriven by a drive mechanism (not shown) for plasticization of the resinas well as is forwardly and backwardly driven by a drive mechanism (notshown) for injection of the molten resin.

The mold is released from the mold clamped state in which the movablemold 105 and fixed mold 104 are closed and clamped together, when amolded article in the mold cavity is cooled and solidified. Then, by theaction of the die plate moving hydraulic cylinder 112, the movable mold105 is separated from the fixed mold 104 and the molded article is takenout.

The movable mold 105 is fitted with a mold temperature sensor 62. Or themold temperature sensor 62 may be fitted to the fixed mold 104 or may befitted to both of the movable mold 105 and the fixed mold 104.

Next, the mold temperature adjusting apparatus 1′ will be described.

Like in the first embodiment, a low temperature water tank 3 comprises alow temperature water temperature adjusting means (not shown) adjustingthe temperature of the low temperature water to a set low temperature. Alow temperature water supply piping 31 a elongates from a bottom portionof the low temperature water tank 3 to be connected to heat mediuminlets of the fixed mold 104 and movable mold 105 via a low temperaturewater transfer pump 6, a low temperature water supply piping 31 c, a lowtemperature water supply opening/closing valve 52 and a low temperaturewater supply piping 31 d.

On the other hand, a low temperature water return piping 35 a elongatesfrom an upper portion of the low temperature water tank 3 to beconnected to heat medium outlets of the fixed mold 104 and movable mold105 via a low temperature water return opening/closing valve 55 and alow temperature water return piping 35 c.

A low temperature water temperature sensor 63 is provided on the lowtemperature water tank 3 for detecting temperature of the lowtemperature water as a heat medium in the low temperature water tank 3.Output of this low temperature water temperature sensor 63 is used for acontrol to maintain the temperature of the low temperature water in thelow temperature water tank 3 to the above-mentioned set low temperature,more concretely, for a control of quantity of a cooling medium flowingthrough the low temperature water temperature adjusting means of the lowtemperature water tank 3.

A high temperature water tank 4 comprises a high temperature watertemperature adjusting means (not shown) adjusting the temperature of thehigh temperature water to a set high temperature. A high temperaturewater supply piping 41 a elongates from a lower portion of the hightemperature water tank 4 to be connected to the low temperature watersupply pump 31 d via a high temperature water transfer pump 8circulating the high temperature water and a high temperature watersupply opening/closing valve 53.

Also, a high temperature water return piping 42 b elongates from anupper portion of the high temperature water tank 4 to be connected at areturn piping jointing portion A to the high temperature water returnpiping 35 via a high temperature water return opening/closing valve 54.

A high temperature water temperature sensor 64 is provided on the hightemperature water tank 4 for detecting temperature of the hightemperature water in the high temperature water tank 4. Output of thehigh temperature water temperature sensor 64 is used for a control tomaintain the temperature of the high temperature water in the hightemperature water tank 4 to the set high temperature, more concretely,for a control of quantity of a heating medium flowing through the hightemperature water temperature adjusting means of the high temperaturewater tank 4.

By operating the high temperature water transfer pump 8 in the statethat the low temperature water supply opening/closing valve 52 and lowtemperature water return opening/closing valve 55 are closed and thehigh temperature water supply opening/closing valve 53 and hightemperature water return opening/closing valve 54 are opened, the hightemperature water from the high temperature water tank 4 flows throughheat medium passages in the fixed mold 104 and movable mold 105 so thatthe fixed mold 104 and movable mold 105 are heated.

At this time, if operation of the low temperature water transfer pump 6is continued, as the low temperature water fed into the feed side piping36 from the low temperature water tank 3 returns into the lowtemperature water tank 3 through the low temperature water return piping37 b of which flow passage is throttled by the low temperature waterpressure adjusting valve 61, a hydraulic pressure in the feed sidepiping 36 is elevated to a predetermined value. The feed side piping 36is connected to a lower portion of a heat recovery tank 25 and an upperportion of this heat recovery tank 25 communicates with the hightemperature water tank 4 via a high temperature water transfer piping44. Hence, the hydraulic pressure in the feed side piping 36 acts on theinterior of the high temperature water tank 4 via the heat recovery tank25 to thereby elevate a saturation vapor pressure of the hightemperature water in the high temperature water tank 4. Thus, thetemperature of the high temperature water becomes possible to beadjusted and maintained to 100° C. or higher.

By closing the high temperature water supply opening/closing valve 53and high temperature water return opening/closing valve 54 and bystopping the operation of the high temperature water transfer pump 8,circulation of the high temperature water is stopped. Then, by openingthe low temperature water supply opening/closing valve 52 and lowtemperature water return opening/closing valve 55, the low temperaturewater from the low temperature water tank 3 is circulated to flowthrough the fixed mold 104 and movable mold 105 so that the fixed mold104 and movable mold 105 can be cooled.

The heat recovery tank 25 connected to the high temperature water tank 4via the high temperature water transfer piping 44 is formed in alongitudinally elongating cylindrical shape having an inner volumelarger than the total of inner volumes of heat medium flow passages ofthe fixed mold 104 and movable mold 105 and inner volumes of the hightemperature water supply piping 41 a, low temperature water supplypiping 31 d, low temperature water return piping 35 a (between the heatmedium outlets of the fixed mold 104 and movable mold 105 and the returnpiping jointing portion A) and high temperature water return piping 42b. Thereby, the heat recovery tank 25 functions to suppress mixing ofthe high temperature water and low temperature water.

The mold temperature adjusting apparatus 1′ constructed as mentionedabove is controlled by the molding machine control unit 115 and the moldtemperature control unit 132 associated therewith, as follows:

In FIG. 15, mechanical parts and components arranged integrally oradjacently are collectively shown. Also, pipings (heat medium pipingsand hydraulic pressure pipings) are shown by double lines and electricalsignal wirings by single lines.

In FIG. 15, the mold temperature control unit 132 comprises a centralcontrol processing unit (CPU), a storage circuit storing set values,measured values, display image data, etc. and an input/output circuit.An image displaying panel (This is sometimes referred to as an injectionmolding condition setting and image displaying panel.) 133 as well as asetting means 146 are provided being kept at hand of operator. The imagedisplaying panel 133 comprises a touch key type image displaying panelas shown in FIG. 16.

In the display image of the image displaying panel 133, a moldtemperature set position, timer operation start position, etc. in themolding step can be specified by touch keys. Set values of temperature,time, etc. are inputted by a numeric keypad provided in the settingmeans 146.

The mold temperature control unit 132 makes comparison between thetemperature of the low temperature water in the low temperature watertank 3 detected by the low temperature water temperature sensor 63 andthe low temperature water temperature set value set by the setting means146 (that is, TLW shown in FIG. 16) and adjusts a flow rate of thecooling medium to be fed into the low temperature water temperatureadjusting means (heat exchanger) of the low temperature water tank 3 sothat no deflection is caused between these two temperatures, or so thatthe temperature of the low temperature water in the low temperaturewater tank 3 is maintained to the low temperature water set lowtemperature. It is to be noted that the flow rate of the cooling mediumis adjusted by controlling an electromagnetic valve (not shown).

Likewise, the mold temperature control unit 132 makes comparison betweenthe temperature of the high temperature water in the high temperaturewater tank 4 detected by the high temperature water temperature sensor64 and the high temperature water temperature set value set by thesetting means 146 (that is, THW in FIG. 16) and adjusts a flow rate ofthe heating medium to be fed into the high temperature water temperatureadjusting means (heat exchanger) of the high temperature water tank 4 sothat no deflection is caused between these two temperatures, or so thatthe temperature of the high temperature water in the high temperaturewater tank 4 is maintained to the high temperature water set hightemperature. It is to be noted that the temperature of the hightemperature water can be stably maintained to a set high temperature of100° C. or higher by elevating a saturation temperature of steam in thehigh temperature water tank 4 by a hydraulic pressure adjusting functionof the low temperature water pressure adjusting valve 61.

The molding machine control unit 115 controls to change over thehydraulic pressure change-over valve 116 in accordance with a program ofthe molding steps so as to feed working fluid into the respectivehydraulic cylinders sharing in the molding steps of the injectionmolding machine and also controls to drive a motor to rotationally drivethe injection screw 107 for plasticization of the resin.

The mold temperature control unit 132 makes comparison between theactual temperature of the fixed mold 104 and movable mold 105 detectedby the mold temperature sensor 62 and a set temperature (This is atarget temperature set by the setting means 146.) of the fixed mold 104and movable mold 105 corresponding to each of the molding steps and,when the actual temperature of the fixed mold 104 and movable mold 105coincides with the set temperature corresponding to the respectivemolding steps, instructs the molding machine control unit 115 to proceedto the next molding step as well as instructs the mold temperatureadjusting apparatus 1′ to set the timer so as to decide the timing tochange over the heat medium to be fed into the fixed mold 104 andmovable mold 105 or to change over the heating and cooling of thesemolds 104, 105.

Next, the molding steps of the injection molding machine and functionsof the mold temperature adjusting apparatus 1′ associated therewith willbe described with reference to FIGS. 14 to 17.

In order to carry out the heating of the fixed mold 104 and movable mold105 before filling the molten resin or the cooling of the fixed mold 104and movable mold 105 after filling the molten resin, the setting means146 previously sets the high temperature water temperature set valueTHW, low temperature water temperature set value TLW, heatingover-shooting temperature correction value ΔTH at the time of heatingthe mold, cooling over-shooting temperature correction value ΔTL at thetime of cooling the mold, resin filling start mold temperature TH at thetime to start the filling step, mold opening start temperature TL at thetime to finish the cooling and high temperature heat medium supply starttemperature set value ΔTL2 at the time to start the supply of the hightemperature water after stopping the supply of the low temperaturewater.

By the way, in a substance having a large thermal capacity, such as thefixed mold 104 and movable mold 105, the heat transmission velocity isslow.

For this reason, even if the feed of the heat medium is stopped at thetime when the temperature of the fixed mold 104 and movable mold 105 hasreached the set temperature, such a phenomenon occurs that thetemperature still changes. That is, at the time of heating, such aphenomenon occurs that the temperature of the fixed mold 104 and movablemold 105 exceeds the set temperature after the feed of the heat mediumis stopped (over-shooting phenomenon). Also, at the time of cooling,such a phenomenon occurs that the temperature of the fixed mold 104 andmovable mold 105 becomes lower than the set temperature after the feedof the heat medium is stopped (under-shooting phenomenon).

The above-mentioned heating over-shooting temperature correction valueΔTH and cooling under-shooting temperature correction value ΔTL mean anelevated temperature and a lowered temperature, respectively, of thefixed mold 104 and movable mold 105 after the feed of the heat medium isstopped.

In order to set the high temperature water temperature set value THW,low temperature water temperature set value TLW or other values,operator touches respective rectangular frames designated with the hightemperature water temperature set value THW, low temperature watertemperature set value TLW, etc. in the image of the image displayingpanel 133 (FIG. 16) and then inputs numerical values in the respectiveframes by a numerical keypad provided on the setting means 146.

The heating over-shooting temperature correction value ΔTH is apredicted elevated temperature value restricting the timing to stop thefeed of the high temperature heat medium so that over-shooting of thetemperature of the fixed mold 104 and movable mold 105 is suppressed.Also, the cooling under-shooting temperature correction value ΔTL is apredicted lowered temperature value restricting the timing to stop thefeed of the low temperature heat medium so that under-shooting of thetemperature of the fixed mold 104 and movable mold 105 is suppressed.

These heating over-shooting temperature correction value ΔTH and coolingunder-shooting temperature correction value ΔTL can be predicted by thefollowing method.

That is, in the state that the mold is not filled with the resin (drycycle), the fixed mold 104 and movable mold 105 are heated and cooledand a time constant of temperature changes of the fixed mold 104 andmovable mold 105 is actually measured. This time constant corresponds tothe thermal capacity of the fixed mold 104 and movable mold 105 and thelarger is the time constant, the more remarkable become theabove-mentioned over-shooting and under-shooting. Hence, based on thistime constant, the heating over-shooting temperature correction valueΔTH and cooling under-shooting temperature correction value ΔTL arepredicted to be set.

In the image displaying panel 133, an actually measured wave shape ofthe mold temperature changes in case the mold as a single unit is heatedand cooled (dry cycle) can be displayed as an image in a screen of theimage displaying panel 133. Where a sample mold is used as the mold 2,in a dry cycle using high temperature water of 145° C. and lowtemperature water of 22° C., temperature of the mold 2 is elevated andlowered. The result of measurements of the temperature is then displayedin the image of the image displaying panel 133 in which the injectionmolding conditions are set, as exemplified in FIG. 17.

FIG. 17 is a schematic view showing one example of an image showing anactually measured wave shape of temperature changes of the mold 2 whenthe mold 2 as a single unit is heated and cooled for setting initialmolding conditions. From FIG. 17, a mode of changes of the temperatureelevation and temperature lowering of the mold 2 can be known and thisserves to shorten the molding conditions.

Where the mold temperature at the time of starting the injection is 120°C., if the temperature change at the time corresponding to thetemperature of around 120° C. is seen, a temperature elevation of 15° C.in 5 seconds is observed. Also, around the temperature of 70° C. at thetime of stopping the cooling, a temperature lowering of 20° C. in about10 seconds is observed.

Thus, based on such temperature changes of the mold and such temperatureelevation and lowering, the mold temperature control unit 132 calculatesthe time constant and, based on this time constant, predicts the heatingover-shooting temperature correction value ΔTH and coolingunder-shooting temperature correction value ΔTL.

(Operation of Mold Heating)

The mold temperature control unit 132 judges whether or not the measuredvalues detected by the low temperature water temperature sensor 63 andhigh temperature water temperature sensor 64 have reached the settemperatures of the low temperature water temperature set value TLW andhigh temperature water temperature set value THW, respectively, in thestate that all the opening/closing values 52 to 55 are closed and, uponconfirming that the measured values have reached the respective settemperatures, controls to open the high temperature water supplyopening/closing valve 53 and high temperature water returnopening/closing valve 54 as well as to start operation of the hightemperature water transfer pump 8. Thereby, the high temperature wateris supplied into the fixed mold 104 and movable mold 105.

Then, as soon as the CPU of the mold temperature control unit 132 judgesthat the mold temperature has reached the high temperature fluid stoptemperature TH−ΔTH (see FIG. 16), based on a command from this CPU, thehigh temperature water supply opening/closing valve 53 and hightemperature water return opening/closing valve 54 are closed and thehigh temperature water transfer pump 8 is stopped. Thereby, the supplyof the high temperature water into the mold is stopped.

(Operation of Resin Filling and Mold Cooling)

The injection unit 110 is in a stand-by position in the state that themolten resin is accumulated in a terminal end portion of the injectioncylinder 106.

When the mold temperature is elevated by the heating over-shootingtemperature correction value ΔTH beyond the high temperature fluid stoptemperature TH-ΔTH to reach the resin filling start mold temperature TH,a screw operating command signal is sent to the molding machine controlunit 115 from the mold temperature control unit 132. Thereby, theinjection screw 107 is operated to advance toward the mold and thefilling step to fill the resin into the mold cavity is started.

The fact that the temperature of the fixed mold 104 and movable mold 105has reached the resin filling start mold temperature TH can be known byan output of the mold temperature sensor 62. But the over-shooting timeS1 (hereinafter sometimes referred to as a high temperature maintainingtime set value) in which the temperature of the fixed mold 104 andmovable mold 105 is elevated to the resin filling start mold temperatureTH from the high temperature fluid stop temperature TH−ΔTH can bepredicted by the time constant actually measured in the above-mentioneddry cycle. Thus, the construction may also be made such that bymeasuring the high temperature maintaining time set value S1 from thetime point when the mold temperature has reached the high temperaturefluid stop temperature TH−ΔTH, the time point when the mold temperaturereaches the resin filling start mold temperature TH is recognized. Inthis case, the high temperature maintaining time set value S1 can bemeasured by the timer.

As soon as the resin filling into the mold cavity is started, the lowtemperature water supply opening/closing valve 52 and high temperaturewater return opening/closing valve 54 are opened by the mold temperaturecontrol unit 132. Thereby, the low temperature water is supplied intothe fixed mold 104 and movable mold 105 so that the high temperaturewater in the heat medium passages of the fixed mold 104 and movable mold105 is discharged to be replaced with the low temperature water.

After the replacement of the high temperature water with the lowtemperature water has been finished (that is, after the high temperaturewater recovery time set value S3, shown in FIG. 16, has passed from thetime point when the low temperature water supply opening/closing valve52 is opened), the mold temperature control unit 132 controls to openthe low temperature water return opening/closing valve 55 as well as toclose the high temperature water return opening/closing valve 54provided in the high temperature water return piping 42 b. Thereby, thelow temperature water is circulated to be supplied into the mold and themold cooling step is commenced.

The above-mentioned high temperature water recovery time set value S3can be predicted by the time constant measured in the above-mentioneddry cycle. Thus, the time point when the replacement of the hightemperature water in the heat medium passages of the fixed mold 104 andmovable mold 105 with the low temperature water is finished can berecognized by measuring the high temperature water recovery time setvalue S3 by the timer.

(Operation of Change-Over the Heat Medium in the Mold and Mold Opening)

When the mold temperature has reached the low temperature fluid stoptemperature TL+ΔTL, the mold temperature control unit 132 controls toclose the low temperature water supply opening/closing valve 52 and lowtemperature water return opening/closing valve 55 to thereby stop thesupply of the low temperature water into the mold. Also, after the moldtemperature has reached a high temperature heat medium supply starttemperature set value TL+ΔTL2 obtained by adding a high temperature heatmedium supply start temperature correction value ΔTL2, which is smallerthan the cooling under-shooting temperature correction value ΔTL(ΔTL2<ΔTL), to the mold opening start temperature TL, or after a lowtemperature maintaining time set value SH, as shown in FIG. 16, that isa time in which the temperature of the fixed mold 104 and movable mold105 lowers to the high temperature heat medium supply start temperatureset value TL+ΔTL2 from the low temperature fluid stop temperatureTL+ΔTL, has passed, the mold temperature control unit 132 controls toopen the high temperature water supply opening/closing valve 53.Thereby, the high temperature water is supplied into the fixed mold 104and movable mold 105 so that the low temperature water in the heatmedium passages of the fixed mold 104 and movable mold 105 is dischargedto be replaced with the high temperature water.

The fact that the temperature of the fixed mold 104 and movable mold 105has reached the high temperature heat medium supply start temperatureset value TL+ΔTL2 can be known by an output of the mold temperaturesensor 62. But the low temperature maintaining time set value SH can bepredicted by the time constant actually measured in the above-mentioneddry cycle. Thus, the construction may also be made such that bymeasuring the low temperature maintaining time set value SH from thetime point when the mold temperature has reached the low temperaturefluid stop temperature TL+ΔTL, the time point when the mold temperaturereaches the high temperature heat medium supply start temperature setvalue TL+ΔTL2 is recognized. In this case, the low temperaturemaintaining time set value SH can be measured by the timer.

When the mold temperature lowers to the mold opening start temperatureTL, a mold opening command signal is sent to the molding machine controlunit 115 from the mold temperature control unit 132. Thereby, the fixedmold 104 and movable mold 105 are opened to be separated from each otherand the molded article is taken out. Thereafter, the fixed mold 104 andmovable mold 105 are closed to be jointed together and keep a stand-bystate.

The fact that the temperature of the fixed mold 104 and movable mold 105has reached the mold opening start temperature TL can be known by anoutput of the mold temperature sensor 62. But the time (under-shootingtime S2) in which the mold temperature lowers to the mold opening starttemperature TL from the low temperature fluid stop temperature TL+ΔTLcan be predicted by the time constant actually measured in theabove-mentioned dry cycle. Thus, the construction may also be made suchthat by measuring the under-shooting time S2 from the time point whenthe mold temperature has reached the low temperature fluid stoptemperature TL+ΔTL, the time point when the mold temperature reaches themold opening start temperature TL is recognized. In this case, theunder-shooting time S2 can be measured by the timer.

(Operation of Mold Re-Heating)

As mentioned above, by opening the high temperature water supplyopening/closing valve 53, the low temperature water remaining in theheat medium passages of the mold is discharged by the high temperaturewater. At the time when the low temperature water is replaced with thehigh temperature water, the high temperature water returnopening/closing valve 54 is opened and the low temperature water returnopening/closing valve 55 of the low temperature water return piping 35 bis closed. Thereby, the circulation for supply of the high temperaturewater is continued and the mold re-heating step is commenced.

The time when the low temperature water is replaced with the hightemperature water can be predicted by the time constant actuallymeasured in the above-mentioned dry cycle. Thus, by measuring suchpredicted time after the high temperature water supply opening/closingvalve 53 has been opened, the time point when the replacement of the lowtemperature water with the high temperature water is finished can berecognized.

The mold temperature control unit 132 causes the image displaying meansto display the actually measured values of the mold temperature in theabove-mentioned steps for each one cycle of the molding steps, as shownin the lower portion of the screen of FIG. 16. Based on this display,the operator makes corrections of the set values of the high temperaturewater temperature set value THW, low temperature water temperature setvalue TLW, heating over-shooting temperature correction value ΔTH,cooling under-shooting temperature correction value ΔTL and hightemperature heat medium supply start temperature correction value ΔTL2so that the molding conditions of the resin by the injection moldingmachine are optimized and the molding cycle is shortened to the minimum.

The injection molding condition setting and image displaying panel 133may also be constructed such that the images of the upper portion andlower portion of the image displaying panel of FIG. 16 are displayedbeing changed over to each other on the same one screen. By so doing,the injection molding condition setting and image displaying panel 133can be made small sized and less expensive.

According to the present second embodiment, the high temperature watertemperature set value THW, low-temperature water temperature set valueTLW, heating over-shooting temperature correction value ΔTH and coolingunder-shooting temperature correction value ΔTL can be respectivelyappropriately set and thereby the molding cycle can be shortened to theminimum. Also, in the displaying panel of the image displaying panel133, the set values and actually measured values of the mold temperaturefor each of the molding steps of the molding machine can be comparedwith each other. Thereby, an optimal change pattern of the moldtemperature can be easily set.

Third Embodiment

Next, a third embodiment of a mold temperature adjusting apparatus 1″and method according to the present invention will be described withreference to FIGS. 18 and 19.

The present third embodiment is substantially the same as the secondembodiment except that the injection molding condition setting and imagedisplaying panel 133 and setting means 146 shown in FIGS. 14 and 15 areeliminated and their functions are taken charge of by the setting anddisplaying means 115 a.

That is, the setting and displaying means 115 a comprises an imagedisplaying panel of touch key type as shown in FIG. 16, on which theimage of FIG. 16 is displayed when a first display mode is set byoperation of touch keys or the like.

In this case, the mold temperature set positions, timer operation startpositions, etc. in the molding steps, as mentioned above, can bespecified by touch keys and set values of temperature, time, etc.corresponding to the positions so specified can be inputted by a numerickeypad (not shown).

The set values of the mold temperature control condition displayed onthe injection molding condition setting and image displaying panel 133are transferred to the mold temperature control unit 132 from themolding machine control unit 115 so that the above-mentioned control ofthe mold temperature is carried out.

Also, the actually measured values of the mold temperature aretransferred to the molding machine control unit 115 from the moldtemperature control unit 132 to be displayed on the injection moldingcondition setting and image displaying panel 133, as shown in the lowerportion of FIG. 16.

On the other hand, when a second display mode is set by operation oftouch keys or the like, an image for setting the molding conditions isdisplayed on the injection molding condition setting and imagedisplaying panel 133. In this case, set positions of the moldingconditions, such as an injection pressure, injection velocity, pressuremaintaining time, etc, can be specified by touch keys and set valuescorresponding to the positions so specified can be inputted by thenumeric keyboard.

Based on the set values displayed on the injection molding conditionsetting and image displaying panel 133, the molding machine control unit115 controls a drive hydraulic pressure of the die plate movinghydraulic cylinder 112, mold clamping hydraulic cylinder 102 a,injection screw 107, etc. and also causes the actually measured valuesof the injection pressure, etc. to be displayed on the injection moldingcondition setting and image displaying panel 133.

According to the present third embodiment, by selecting the firstdisplay mode, set values, of the mold temperature control conditions andactually measured values of the mold temperature can be displayed. Also,by selecting the second display mode, set values of the moldingconditions and actually measured values of the injection pressure,injection velocity, etc. can be displayed. Thereby, workability of theoperator can be enhanced. Also, neither an image display means nor asetting means is needed to be provided on the mold temperature controlunit 132 and a cost reduction of the apparatus can be realized.

In the above, while several examples of the mold temperature adjustingapparatus and method as well as the mold temperature control unit of thepresent invention have been described based on the embodiments, thepresent invention is not limited thereto but, needless to mention, maybe added with various modifications in the concrete structure within thescope of the claims of the invention as appended herein.

For example, in the mold temperature adjusting apparatus of theembodiments according to the present invention, while the examples ofusing water as the heat medium have been described, the heat medium isnot limited thereto but various fluids other than water, such as oil,steam or the like, can be used.

1. A mold temperature adjusting method using a high temperature fluidsupply system (41) supplying a fluid of high temperature into a mold(2), a low temperature fluid tank (3), a low temperature fluid transferpump (6,7), a low temperature fluid supply system (31) supplying thefluid into said mold (2) from said low temperature fluid tank (3), a lowtemperature fluid return system (35) returning the fluid into said lowtemperature fluid tank (3) from said mold (2) and a low temperaturefluid by-pass system (40) connecting said low temperature fluid supplysystem (31) and said low temperature fluid return system (35) to eachother so that a control of a mold temperature of said mold (2) iseffected by a high temperature heat medium and low temperature heatmedium predetermined temperatures being selectively caused to flow in aheat medium passage provided in said mold (2), wherein said moldtemperature adjusting method includes the steps of: actually measuring amold temperature of said mold (2); and while said mold (2) is heated,stopping supply of the high temperature heat medium into said mold (2)through said high temperature fluid supply system (41) when the moldtemperature is elevated to a high temperature fluid stop temperatureTH−ΔTH obtained by subtracting a heating over-shooting temperaturecorrection value ΔTH from a predetermined resin filling start moldtemperature TH and while said mold (2) is cooled, stopping supply of thelow temperature heat medium into said mold (2) through said lowtemperature fluid supply system (31) when the mold temperature islowered to a low temperature fluid stop temperature TL+ΔTL1 obtained byadding a cooling under-shooting temperature correction value ΔTL1 to apredetermined mold opening start temperature TL, said heatingover-shooting temperature correction value ΔTH being a predictedelevated temperature value regulating a supply stop timing of the hightemperature heat medium so that over-shooting of the mold temperature issuppressed, said cooling under-shooting temperature correction valueΔTL1 being a predicted lowered temperature value regulating a supplystop timing of the low temperature heat medium so that under-shooting ofthe mold temperature is suppressed, wherein the supply of the hightemperature heat medium into said mold (2) is started when the moldtemperature is lowered to a high temperature heat medium supply starttemperature set value TL+ΔTL2 obtained by adding a high temperature heatmedium supply start temperature correction value ΔTL2, which is smallerthan the cooling under-shooting temperature correction value ΔTL1(ΔTL2<ΔTL1), to the mold opening start temperature TL and the supply ofthe low temperature heat medium into said mold (2) is started when themold temperature is elevated to the resin filling start mold temperatureTH.
 2. A mold temperature adjusting method as claimed in claim 1,wherein a progress of temperature elevation corresponding to the heatingover-shooting temperature correction value ΔTH is recognized by a moldtemperature sensor (62) actually measuring the mold temperature or by atimer means measuring an over-shooting time S1 predicted as needed forthe mold temperature to be elevated to the resin filling start moldtemperature TH from the high temperature fluid stop temperature TH−ΔTHas well as a progress of temperature lowering corresponding to thecooling under-shooting temperature correction value ΔTL1 is recognizedby said mold temperature sensor (62) actually measuring the moldtemperature or by a timer means measuring an under-shooting time S2predicted as needed for the mold temperature to be lowered to the moldopening start temperature TL from the low temperature fluid stoptemperature TL+ΔTL1.
 3. A mold temperature adjusting method as claimedin claim 2, wherein said over-shooting time S1 is predicted based on atime constant of temperature changes of said mold (2) when said mold (2)as a single unit is heated as well as said under-shooting time S2 ispredicted based on a time constant of temperature changes of said mold(2) when said mold (2) as a single unit is cooled.
 4. A mold temperatureadjusting method as claimed in claim 1, wherein the time when the moldtemperature is lowered to the high temperature heat medium supply starttemperature set value TL+ΔTL2 is recognized by a mold temperature sensor(62) actually measuring the high temperature heat medium supply starttemperature set value TL+ΔTL2 or by a timer means measuring a lowtemperature maintaining time set value SH predicted as needed for themold temperature to be lowered to the high temperature heat mediumsupply start temperature set value TL+ΔTL2 from the low temperaturefluid stop temperature TL+ΔTL2.
 5. A mold temperature adjusting methodas claimed in claim 1, further including the steps of: setting moldtemperature control conditions of the temperatures of the hightemperature heat medium and low temperature heat medium, resin fillingstart mold temperature TH, heating over-shooting temperature correctionvalue ΔTH, mold opening start temperature TL, cooling under-shootingtemperature correction value ΔTL1 and high temperature heat mediumsupply start temperature correction value ΔTL2; and displaying on aninjection molding condition setting and image displaying panel (133) afirst image showing a reference mold temperature curve of a molding stepadded with the mold temperature control conditions and a second imageshowing actually measured temperature changes of said mold (2) in anactual molding step.
 6. A mold temperature adjusting method as claimedin claim 1, wherein said heating over-shooting temperature correctionvalue ΔTH is predicted based on a time constant of temperature changesof said mold (2) when said mold (2) as a single unit is heated and saidcooling under-shooting temperature correction value ΔTL1 is predictedbased on a time constant of temperature changes of said mold (2) whensaid mold (2) as a single unit is cooled.